How do I change the positive battery terminal

Hyundai/Kia tend to have modular terminals on the newer 2010+ cars - not all, but a lot went in that direction. That said, the first thing I usually do is clean it with barkeepers friend and a wire brush - it usually recovers the terminal. If the damage is beyond this, then you need to take the terminal block apart and clean it in vinegar, then neutralzie it in a mix with baking soda and water - ratio doesn't matter, just make sure it's more baking soda vs water. If that fixes it, then you're good to go.

If the terminal is unrecoverable, KiaPartsNow has them: https://www.kiapartsnow.com/genuine/kia-...