How do I find a union? I don’t see anything relating to unions in the workplace.

I’m a little scared and I would like to join a union. My boss is getting chewed out for overtime hours worked so he is telling some of the employees to stop coming in so early, but there are some that do come in early and are told not to clock in until a certain time, some employees of which have to come in due to us being short staffed. Normally when we have someone who can’t make it I’m the one they call, I’m just afraid they might try to take hours from my check.