I used to work as a residential electrician, and now work in industry. I would get a generator, and have an electrician go out there and set up some type of disconnect or hang a plug out of the panel that is wired the cable the goes to the generator, plus ground the trailer.
My concern came when I read your description of big black wires and a white one. Need to ground it properly and terminate the cables correctly. Rain proof.
Seen alot of hack stuff out there by handyman.
I am the kind that refuses to pay someone else to do it, but I also put alot of time in reading how to do it correctly. There are nuances to electrical, as with any trade.
You may want to just hang a plug out of the panel, or put a post in the ground with a disconnect. Myself, I am not worried about code as much as I am safety.