Breakers are for 120vac, And you won't find any on the converter, FUSES are for 12VCD, and if one door covers both breakers and fuses (Note if inside a cupbord or cabinet the outer door does not count) then the converter is very likely BEHIND that panel (part of the assembly)
Breakers and fuses are in power distribution centers.
So turning off breakers does not turn off 12vdc.. There may be a DISCONNECT (May say Use/Store or Aux Battery) switch just inside the door, often accessable while standing on the ground.
FOr long term storage.. Lift NEGATIVE leads off battery.