I can see the ladders used in the brochure for my Coleman. Find the brochure for your unit and see if that will help. It's going to be a guessing game unless you can find another exact unit like yours.
You will probably need to drill exploratory holes to find the exact mounting braces. Then you can fill those holes in that are not used.
Sad to say, Coachman had not responded to my request 3 years ago for technical information for my unit. Things like wiring schematics, ladder brace placement, etc..
Very poor customer relations in my opinion. Or should I say..." No customer relations"....
2015 Sierra 1500 Denali
2014 Coleman 249RB
David Jon Devoucoux
People, Places & Things...for over 40 Years!