Hi guys i have one problem, i dont have lights roof and door, i tesy voltage and i dont have power 12V, can you tell me where start. can you tell me where the initial plug / beam is located?

and I do not have a backlight, but with the gearbox, on the right I have a free plug, is it for this lamp? if so where is the cable to go? because on the gearbox near the engine compartment I have 3 free plugs, is it normal?