What kind of turtle is this?

I found a baby turtle the other day. It is the size of a half-dollar with a brown shell that has 3 spikes going down the center of the shell that are a light brown and on its under belly it has a yellow like growth in the center and the underbelly is dark brown with the edges being light brown it has clawed feet and a pointed nose. if anyone could help that would be great i just need to find out what it is so i can feed him and release him once hes big enough to survuve. Thanks so much.