I don't know my pin code for my Mac book air how can I get it?

If you bring it to the Apple Store with Proof of Purchase, they can reset it for you.

HI,my mac is locking 3 or 4 months. I'm an English teacher,so i have a lot of work with my mac for my classes.I'm very nnervous and angry for that problem. I don't know what Is my pin code. what am i do?????!!!!!!!! Help me please