The white wire normally goes to a bolt in the frame (make sure).
That should be ground. It gets hooked up last.
Follow the other wires and look for a current limiter that may have a red cover; that is normally positive. (I am guessing that red is the main DC power wire in your camper)
The others are most likely your powered tongue jack and powered stabilizers (if you have them) or a powered slide/top, but a volt meter should tell you if any are also ground.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW