As others have said the center pin of your plug should be for back up lights. When I mounted lights on the back of my 5th I wired them with a relay so the power is taken from the trailer battery. My 5th was wired up to the pin box so I had to run a wire from there back. Another idea I had was to mount a light on each side facing back just in front of the wheels. I have these on a switch so if I have to maneuver back and forth in the dark I can keep an eye on how the trailer is doing even when the backup lights are off.