A few things. The power coming into your house is grounded

[Bruno1949]

somewhere. Hopefully a ground rod. Grounding to a water pipe is very out of date but still exists. Follow the ground from your main breaker box and bolt a ground wire from your generator to that ground. Do not just wrap it around the pipe or whatever. It has to be mechanically bonded to the ground. Bolts, clamps, something solid.

Also, to save the life of your utility workers, install a proper change over switch next to your breaker panel. I know it’s expensive, but if you put 220 volts into the main lines the transformer down the street turns into 2400 volts. It will kill a worker down the lne unless you only use extension cords to connect to the generator.