Unless an inverter was added by a previous owner, you don't have one on a 2009 Bighorn. Some years later, maybe on 2014 models, Heartland began offering Residential Refrigerators with an accompanying small inverter for the fridge.
If you don't want to use a generator, you'll need to add an inverter, wiring to the outlets you want powered, probably more batteries, and some way to charge up the batteries - perhaps Solar.