Where is the wiring harness for a 2008 Buick Enclave?

I am going to put a trailer hitch receiver on an 2008 Buick Enclave. Any one know where the wiring harness is under the vehicle for the 4 prong plug?|||It is not factory installed and you need the harness as well as the jumper box.Sorry for your luck.|||Should be near the rear bumper in wires leading to tail lights