Anyone know a good tutorial to learn how to clean up 3d scans / AI rendered STL?

I just discovered makerworld has a 2d image to 3d model converter https://makerworld.com/en/makerlab/imageTo3d?from=makerlab but they look all weird and crumpled , with random holes etc- I tried to google videos on the topic but nothing useful came up. What kind of tutorials or techniques should I be looking up? And any tips?