Precaution if you don't know DO NOT RUN YOUR GENERATOR WITH POWER STILL SUPPLIED TO THE GRID/MAIN POWER LINES
Best choice if you have an electric dryer, is to simply pull your dryer out & plug your generator into the dryer socket with a long cord (ie you don't want fumes in your house). Usually those are 30 Amp sockets with a built in breaker/fuse in your panel. You can simply shut off the power in your main/outside breaker to the house until power resumes to the neighborhood.
If you can go this route & thave the ability/room in your main breaker box, add a shut off to the main power lines (ie from the street) right there so you don't need to go outside. My F-I-L set my last home up with me to easily shut off power to the street when running a generator in our last home that we remodeled before moving. This new one doest have room & I need to shut off power in the outside main box before hooking my generator up to my main box outside.
Luckily I have room for a 50 amp breaker that can be turned on & shut off the city power when my generator in manually turned on. My F-I-L convinced me to do it this way instead of trying to tie into another plug since all of mine are 15 or 20 amps due to my kitchen & dryer running on natural gas. This will let you run your house normally (limiting how much power you use) without redoing stuff inside.
As a homeowner that is confident building (helped with many complete remodels) IF this pump was on it's own breaker, I would simply add/splice an outlet into the line (outlet amps should match the breaker amps to prevent fire), I would also use a GFCI to be safe (though that may trip if putting a generator into it). I assume from what you said that it is hardwired in & splicing in could work, but is the least effective way to gerryrig the project. Unless you have a very small generator, it really is just best to hook up to your electric dryer outlet if possible, or the main box outside from what I have seen.
I cannot stress enough that you do not want to feed power to the main lines. You will power all the neighbors before your generator potentially dies & worse it can send electricity into the lines that workers will be trying to fix & hit them
edit- If your main concern is the sewage pump, consider a large LiPo battery that can be charged via portable solar panels that will only power that sewage pump. It will only drain the battery when it kicks on, and solar panels will top it off during the 2-3 days of not being active. I picked up one for about $600 last year IIRC that will power a CPAP in my camper for 10 days with no heater going in the device, it will also charge pretty quickly. Though if your pump only runs once every couple days, it might work with a car battery or two, though it would still be best to get a cheaper deep cycle battery to at least power that pump. Even using it with an inverter to keep your water running could work with panels recharging those batteries over a couple days vs the LiFePo that would charge in half a day. Cheapest setup might be around $300 with battery & a couple panels.
Edit 2- Thinking about plugging into your dryer outlet or electric stove outlet (both 30 amp plug). Hypothetically speaking, maybe consider plugging into a 15 (preferably 20) amp outlet with your smaller generator line & shut off the breaker to the main power line (again don't send power back to the grid) & turn off breakers to all parts that don't need power. Hypothetically speaking, if you only ran the pump, or power to a single 15A set of lights/single small appliance, it would take care of that pump in theory since all the wires in the house would have access to power that you don't turn the breakers off. I mean that is worst case scenario hypothetically.
Precaution if you don't know DO NOT RUN YOUR GENERATOR WITH POWER STILL SUPPLIED TO THE GRID/MAIN POWER LINES
Best choice if you have an electric dryer, is to simply pull your dryer out & plug your generator into the dryer socket with a long cord (ie you don't want fumes in your house). Usually those are 30 Amp sockets with a built in breaker/fuse in your panel. You can simply shut off the power in your main/outside breaker to the house until power resumes to the neighborhood.
If you can go this route & thave the ability/room in your main breaker box, add a shut off to the main power lines (ie from the street) right there so you don't need to go outside. My F-I-L set my last home up with me to easily shut off power to the street when running a generator in our last home that we remodeled before moving. This new one doest have room & I need to shut off power in the outside main box before hooking my generator up to my main box outside.
Luckily I have room for a 50 amp breaker that can be turned on & shut off the city power when my generator in manually turned on. My F-I-L convinced me to do it this way instead of trying to tie into another plug since all of mine are 15 or 20 amps due to my kitchen & dryer running on natural gas. This will let you run your house normally (limiting how much power you use) without redoing stuff inside.
As a homeowner that is confident building (helped with many complete remodels) IF this pump was on it's own breaker, I would simply add/splice an outlet into the line (outlet amps should match the breaker amps to prevent fire), I would also use a GFCI to be safe (though that may trip if putting a generator into it). I assume from what you said that it is hardwired in & splicing in could work, but is the least effective way to gerryrig the project. Unless you have a very small generator, it really is just best to hook up to your electric dryer outlet if possible, or the main box outside from what I have seen.
I cannot stress enough that you do not want to feed power to the main lines. You will power all the neighbors before your generator potentially dies & worse it can send electricity into the lines that workers will be trying to fix & hit them
edit- If your main concern is the sewage pump, consider a large LiPo battery that can be charged via portable solar panels that will only power that sewage pump. It will only drain the battery when it kicks on, and solar panels will top it off during the 2-3 days of not being active. I picked up one for about $600 last year IIRC that will power a CPAP in my camper for 10 days with no heater going in the device, it will also charge pretty quickly. Though if your pump only runs once every couple days, it might work with a car battery or two, though it would still be best to get a cheaper deep cycle battery to at least power that pump. Even using it with an inverter to keep your water running could work with panels recharging those batteries over a couple days vs the LiFePo that would charge in half a day. Cheapest setup might be around $300 with battery & a couple panels.
Edit 2- Thinking about plugging into your dryer outlet or electric stove outlet (both 30 amp plug). Hypothetically speaking, maybe consider plugging into a 15 (preferably 20) amp outlet with your smaller generator line & shut off the breaker to the main power line (again don't send power back to the grid) & turn off breakers to all parts that don't need power. Hypothetically speaking, if you only ran the pump, or power to a single 15A set of lights/single small appliance, it would take care of that pump in theory since all the wires in the house would have access to power that you don't turn the breakers off. I mean that is worst case scenario hypothetically.