Can you get a po box without your parents knowing

My parents are nosy and like to go through my mail. So I wanted to know if I get a p.o box without them ever finding out. I am 19 and I would like to get mail from my friends without them trying to open it.

You're 19, one year into adulthood. As long as you have the money to rent one, go ahead. You're an adult and they have no say in that matter as long as you're paying for it yourself. If this is the case, you don't have to do it secretly as there's nothing wrong to hide.