Find OE number

I had a new valve body put in my transission and now my car won't start. I was told that the computer in my car was taken from another car and does not display my vehicle VIN #. How do I go about finding the OE number for my car. I wanted to purchase an engine computer but I was told that the OE numberr will be needed first. I couldn't give them the OE number from my current computer because if they send me the part it wont work because it would be the wrong OE number. Does anyone know what I should do?

ignore this post, i'm replying to your other post

I am not the original owner. I got the car from the junkyard and fixed it up. It's a 1997 SC2 with about 72,000 miles on it. My car RPm would go up without me putting my foot on the gas and The saturn dealership ran the diagnosis on it and the reading said it had on 2nd, 3rd or 4th gear. The saturn dealership is the one who said it would not start as well.