separate characters's helm from a body

Hi, I'm new here and I hope this the right section.

I have a question, hope I can get helps here. I have never do modeling before and I need some armor for my low poly game. I have these assets... https://assetstore.unity.com/packages/3d/environments/dungeons/polygon-dungeons-pack-102677 Is it possible to take those characters and create a helm from his armor? Then a chest etc etc..? If yes, how and someone have some sources so I can learn. Thanks !