just open the outside hatch door to the WH and look for a black toggle on/off switch that may have a cotter pin in it.
if there isn't one, you probably have a propane-only WH.
didn't you get any paperwork with the trailer? most people keep the manuals for the WH, furnace, fridge, and so on.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC