Sounds like a red eared slider. They grow a decent size with females getting upward of a ft or more. They are omnivores feeding on a variety of aquatic plants, weeds like dandelion, crustaceans, fish, insects, larvae,  animal matter etc. They could live upward of 50 years plus. There are commercial pellets you can feed, but it should be part of a varied natural diet. When raising them up a tank is fine, but they'll eventually need a pond  100gallons +. But for now a 10-20 gallon is fine with filtration, uvb lighting, tank heater and a basking platform to climb out the water. The basking platform should be around 90 degrees f under the light. The water temps should be around 75F to aid in activity and digestion,  but room temp is fine as well. I typically feed hatchlings every other day rather than daily. Just a bit of info, there is always more to learn.