I have an iPhone 4 and I wanna set it up with tmobile?

I have an iPhone 4 that used to have with sprint that let go, I now have tmobile and I'm need of a new phone, so I'm wondering would I be able to get my iPhone set up to use with tmobile

Nope. The iPhone 4, this specific one, is CDMA (Sprint). Can't switch to T-Mobile which is a GSM network.