4 Pin Flat to 6 Pole Round Trailer Wiring Adapter w/ Mounting Bracket
In order to connect the 4-Way Flat Connector on your truck to the 6-Way Round Connector on your trailer, you can use carrofix 6 way round connector.
This adapter allows to plug it into your vehicle's 4 way flat plug and provide a 6 way round connection on the other end. The additional white wire is for ground and will need to be attached to a clean, bare metal surface. The other two wires (Black for 12V power and Blue for brake) from the adapter can simply be tied off and left unused, assuming you only need to power the basic signal lights on the camper.
Wire configuration
Green(4-way flat): Right turn signal and brakes; Yellow(4-way flat): Left turn signal and brakes; Brown(4-way flat): Tail lights; Blue wire: Electric brakes; Black wire: 12V Battery charge; White wire: Ground wire