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.
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Lou & Freya the wonder dog
2008 GMC Sierra 3000HD Allison Duramax
2019 Flagstaff 8529FL