I guess I don't fully understand the problem. I assume you have two battery compartments and all you see in each one is the connectors.
So you will have to understand the wiring to hook up two 6 volts to make 12v.
Find which positive is the load, and find where the ground attaches to your frame. Then hopefully one of the cables between the compartments is a straight run you can use to connect the neg to pos between the batteries. You might have to redo the ground, depending on which side it is on.
Or, better yet if you aren't comfortable doing all that, call an independent RV service shop to help you out.
I'm + you can get it done
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Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD Duramax
Reese Fifth Airborne Sidewinder