First off welcome to irv2 RV Nomad.
2nd here is a link for truck to trailer
wiring. Need also slidein running lights.
Your slidein may not need all the wiring from your truck because if you have a good battery or two, in slide it should be sufficient to keep your refrigerator operating while traveling.
The fridge needs 12v from your battery to operate the control board which operates the LP igniter and gas valves.
If you have a converter that charges it will take care of battery when plugged into shore power wouldn't need trickle charger.
Your fridge will than work off electric heating elements but still need the 12v which will be coming from your converter not battery at this time.
All lights,water pump, HWH & furnace control boards will also work off converter.
You could always get a better converter
with a higher output to add the things you want, added 12v outlets, if you notice your lights dimming when operating items on the 12v curcuits. 12v side of life