If there is a camera up there then you will need to find out some information. Simply plugging in the trail pigtail to your truck isn't going to make it display in your truck.
See if you can find some information about the camera in the package of books/manuals that you got with the trailer. Maybe that can point you in the right direction.
It's either going to be a hardwired camera or a wireless camera. If it's a full wired in camera then you will need to run the wires all the way into the cab of the truck (pretty messy solution if you ask me). If it's wireless then the receiver will need to be hooked up to a monitor in the truck. Best place to go would be a speciality audio shop that does work on 12v car radios and cameras.