can you turbocharge a 3100 SFI V6

Expect to spend $5000-6000 anything can be turbocharged.

If I remember right I think the 3800 grand Prix comes with a supercharger. I would recommend finding one from a scrapyard rebuild the internals and just run the factory supercharger at a higher boost. Now I'm not sure if the mounts and wiring harness are the same but you can get mounts fabed and work with the wiring it'll take some time but it would probably be easier and cheaper.

It will only be slightly cheaper and easier to put a supercharged 3.8 into that car. It can be done, just like turbocharging can be done but every thing has to be changed, including transmission, electronics and fuel system including the fuel pump. If you want a hot rod, a waaaaaay better way to do it is to buy a GTP and do upgrades to it. They are plentiful and inexpensive and companies like ZZ Performance make lots of fascinating upgrades for it. I's move into the 2000 plus range for you choice of year though. Some of the supercharged 3.8s from the mid 90's actually couldn't be upgraded all that easily. I had a '95 Bonneville and there was very little I could do to it without spending major bucks to totally replace the electronics