Installing trailer wiring n need to tap the rear brake wire -asap

I don't know if this is too late, but I believe if you're using a 4-wire connector, the wires are 1) ground, 2) either side parking light, 3) and 4) corresponding left or right turn signal. I don't know the order on the plug. Turn signal lights up when you hit the brakes (and intermittently turns off if you have the turn signal or hazards on). That's how I check the lighting when I'm by myself - first turn on the parking lights, then turn on the hazards.