Its not a cooter Pseudemys sp, its one of the tropical sliders Trachemys, hope you have got either a indoor pond or live in a climate that allows you to set out this guys outdoors when the time comes, they get like 15 inch long or more.
These are very cool turts to have Think a huge RES, thats how they behave. You can also house them outdoors in the summer, tropical they may be but they are no push overs