312QBUD with resi fridge. Question about inverter

lets start with the Inverter brand and model
the info from your owners papers

is there a transfer switch involved ?
the location of the inverter ?

if its hardwired, hidden behind a cabinet etc..
there is NO easy way to use it
pull the fridge out access the wiring box, add another outlet where you can reach it, to plug in and extension cord

if nothing else in the RV has inverter power, then it is a one circuit item, that terminates there, you can NOT easily tie it into the rest of the RV 120v for the outlets