detached garage wiring

i just acquired a house from my in-laws and have what appears to be a really bad wiring issue. I would post an image but I guess I am not allowed.

I have 100 amp service running to the garage from a exterior sub-panel (only has one 100 amp breaker) This is a 3 wire system. Am i correct to assume that the wire with the green insulation would be the ground?

My question is, how could I put a 4 wire panel in the garage? Is it possible? or should I just stay with the 3 wire system?

Michael, we are not a Do-IT-Yourself type of forum and it sounds like you need a qualified electrician to straighten things out for you. Safety is #1

Mess up with Electricity and you could burn everything down or kill yourself. The fact that you asked what the green wire is tells me that you really need to consult an electrician before even thinking about this project.

Edit: Maybe post where you are located and you could get a referral to a local pro.

done and done, Electrician is on the way!

Excellent choice!
Let us know what all he found, if you would. :slight_smile: