How do you convert a 4 way Uhaul Trailer wiring to a 7 way trailer wiring you have a 7 way addapter that hooks to a 4 way you just need to know where to connect the other three wires?

Don't worry about the extra wires, the trailer with a four wire plug doesn't use them. The extra wires left over are for electric trailer brakes, a 12 volt power supply from the tow vehicle and a rarely used back up light or third brake light. The trailer with a four wire plug only uses the white wire for ground, the brown wire for the running lights, the yellow wire for the left signal and brake and the green wire for the right signal and brake.