Uhaul uses their own unique wiring for light hookups.

They sell, or did, an adapter to hook a normal 4 pin wiring setup to their setup.

https://www.uhaul.com/MovingSupplies/Wiring-Lights/Adapters/Trailer-Wiring-Adapters

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.