Can I use a us cellular iphone 5s for att?

Okay, my friend is selling a iphone 5s for us celluar and I have att

I wasn't sure if I could get it and it would still work just as it would if it were att?

And if it can't work is there I way I can unlock it too get it too work and if not could I take it back to us celluar get cash and get one at att?

No. It won't work. US Cellular is a CDMA network and AT&T is GSM

If it is unlocked then it should work. Though I'm not sure if it can be in the case of a CDMA to GSM. In most cases its one or the other but iPhones since the 4s have been both GSM/CDMA.