Not enough information... Is she a big 3 year old, or a little one because it's not so high if she is young and tiny... How high is a temperature that is a little high to you? Does the pain radiate anywhere? How sudden was its onset? Are there any other symptoms? How intense is the pain where her belly hurts? Has she experienced this pain before? What helps or doesn't help the pain? Et cetera. I would seek out medical help in your community rather than on the internet, tbh.