The trailer harness connector is in the center of the van at the rear. It is close to the spare tire. The problem you will encounter is that this harness is not directly complatible with rental trailers. You need a cable pig-tail from Nissan if you don’t have one. The pig-tail will cost you some $$$.
The other way is to do what I did, install a new 4-wire harness terminated with a complatible plug. That’s around $15.00 at Walmart. The signal conversion box is located at the left side of the van inside the removable panel. Run the harness in through a rubber grummet and you can tap the new 4-wires (white, yellow, brown, and black).