The converter can be located in different places. It is commonly mounted in the hall way down close to the floor.
Another common place is along the side of the bed.
It should have 120 circuit breakers on one side. They should be all turned off applying light pressure toward off. Then turn main breaker on if equipped, then branch breakers one at a time.
Next to the 120 volt circuit breakers there maybe a small plate that covers 12 volt power distribution center. The converter in your age of rig is behind the circuit breakers.