I am 18 & I am going to go live with my dad. I have some items that I need to get from my moms house. But, my mom thinks that anything in her house belongs to her. If she was to call the cops for thievery, what would happen?

In order to do things civil , take the police with you and tell them you have things that are your belongings and you want to get them but you don't want your mom to call the police or scream that you stole stuff that wasn't yours . You want be the better person so your best to get the police to escort you in the house to get your stuff and your mom can say everything's hers but you need to take the police so your mom doesn't start doing petty things to stop you from getting your things.