Trunk light doesn't work

My trunk light doesn't work. My first question is how does it turn on in the first place? I heard it might use a mercury switch or something but i have no clue how this works or where its located if thats the case.

My trunk light doesn't work. My first question is how does it turn on in the first place? I heard it might use a mercury switch or something but i have no clue how this works or where its located if thats the case.

replace lamp/measure for voltage, and ground..

replace lamp/measure for voltage, and ground..

I followed the wire and found it was snapped/cut/ripped out somehow..i found this little electrical junction thing in the drivers side trunk well and i found a plastic plug that had no wire going to it so i assumed this is where it went..but when i went to measure for voltage i got nothing. I'll have to check again in the morning because maybe i wasn't getting a good ground