This site won't let me post Thor copyrighted diagrams, but you can get them by registering at the Thor website: https://www.thormotorcoach.com/owner-resource/
You need your coach's VIN.
In general there are two batteries wired in series with jumpers: + to +, - to -. Then there is a black negative cable that goes from a + to a nearby chassis ground post. A red cable goes from one of the + to a 50A breaker, through the on/off switch on mine but to a solenoid on yours and then to the converter. Another red cable goes from a + to the battery isolation system, probably the BIRD type for your coach. A third red cable goes from a + to a 100 amp breaker and then to the generator starter.
That is what is shown on the Thor diagram for my 2021 Axis. Yours may be different.