Your tortise is a baby Chaco Tortoise, Geochelone chilensis. The chaco is a desert scrubland tortoise which while in the wild feeds on grasses, cacti, shrubs, and fruits. In captivity they feed readily on greens such as collard, kale, and grasses for 3/4 of their diet. The rest of the diet can be made up of fruits, vegetables, and even perhaps a little meat as it is speculated that the chaco tortoise feeds on carrion in the wild.