So she didn’t just noticed something and took it, she requested you assist her in retrieving stuff from the house (which garage is part of).

I am confused on what you are having difficulty with. Are you having difficulty saying no to parents? That I totally understand, not easy.

But you seem having difficulty understanding that it’s just not ok to take things from ex spouse’s place if you don’t live there anymore. You don’t even think taking stuff from garage is the same as taking from the house. I am puzzled. If you ever live independently I worry that people will take advantage of you (roommates, neighbours, housemates etc)