last month I installed a camera on our 2932RL 5th wheel. The trailer came from the factory with camera prep for Voyager brand cameras. I believe your 2108TB has the same setup. The cover plate Looks similar in the video I watched but I couldn't make out the white text on the black plate below the marker lights on the rear of the 2108. If it says Voyager, you should have what I had.
When i removed that plate (4 screws) I found a hole under it containing a 4 pin electrical connector. 1 pin was hot, one ground, 2 were empty. The hot pin is hot if the DC power is turned on in the trailer. It is not powered by marker lights. There was no video cable strung through the trailer, just power and ground.
As RocknRoll suggested, get a ladder and check.
I installed a haloview wireless camera. The version I ordered included the signal amplifier and long cable to allow the antenna to be mounted on the front of the trailer roof. The standard haloview kit comes with brackets and wiring to connect to a trailer with furrion camera prep. I had to buy a separate bracket to bolt to a voyager prepped trailer. I think the voyager cable came with the camera. I ordered direct from haloview. The voyager cable plugged right into the connector in the trailer.
The camera was well worth the money. It's so nice to be able to glance at the rear view mirror and see the traffic behind me rather than a white wall.
I have not tried to use it while backing though. I use the side mirrors and a spotter for that.