I can't find a manual for my camper
Even if you could and there was one, you would likely be surprised that it would be very generic.
The sub-systems and components all come from the same handful of suppliers. Usually a component-specific manual can be found online.
There are a lot of videos on youtube that should explain most issues. A generic video for a class C RV will explain many things, most information on the operation of an RV is not truck camper specific.
But it would be best if you could find someone locally who walks you through your camper and assists with first-time loading and unloading the camper.
It is not rocket science, you will be fine.