My brother is stealing my snacks

I make my lunch in the morning and don't like scavenging the kitchen for snacks so last time my dad and i went shopping I grabbed these snack bags. Now they are in the kitchen and my brother keeps taking them and I asked him to stop, but he didn't and my dad took the snacks and hid them. I explained to him why I needed the snacks for school, but he dismissed me. What should I do?