In order to connect the RV blade 7 way round trailer socket on your vehicle to the 5 pin flat plug on your trailer, you may use carrofix 7 blade round to 5 way flat connector.
This adapter allows you stretch 2 to 3 feet long so you can connect your 7-way vehicle-end connector to a 5-way flat plug on your trailer. Constructed with heavy duty abrasion resistant coiled cable would effectively prevent wires from dragging on ground. Perfect for running power from your vehicle - with the 7-way RV plug - to a trailer with a 5-way flat plug.