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There are 2 items concerning the trailer braking and lighting system. 1) to answer your question, near your trailer hitch, or where the hitch should be, there is an electrical plug-in set up within 6 inches to a foot of where the trailer ball sits (the receiver or trailer hitch). It's there so you can connect the trailer lighting and trailer brakes (if so equipped) to the vehicle lighting and braking system. The trailer electrical just plugs into it. 2) having a factory towing package on the burb does not necessarily mean that you have the electrical brake set-up. You could have lights only, meaning running lights, turn flashers and stop lights. But, if you have electrical trailer braking, you will have a controller installed in, or most probably, under the dash board. You'll know if it's there because it's within easy reach while driving (so driver can apply extra braking if needed) and you've probably bumped your knee into it while entering or exiting the vehicle.
So, if you don't have a trailer braking controller (electrical brakes), you need only be concerned (at this point) with the wires on the rear of vehicle, from tail lights and rearward.