Ask HN: Can you ask someone to be your mentor? How do/did you find one?

I read a lot about how a great asset it can be to have a mentor when you want to be an entrepreneur. Today as a young entrepreneur (20yo), I'm asking myself if I should have a mentor. I know a lot of people in the business and I would love to have someone especially as a mentor, I often talk to him, he gives me some advices but it's not mentoring though. So I'm asking HN the question, should I ask him to be my mentor or just see if it comes up some day, how do people do usually ? Is it different whether it's in the US or in Europe ? Also if you have a mentor, how did you find yours ?