See Who's Following You in Facebook
If you've allowed people to follow you, you can see a list of your followers by going to your profile, clicking Friends below your cover photo and then clicking Followers. If you don't have any followers, you won't see this option.
Note: If you let people who aren't your friends follow you, people who send friend requests that you ignore, delete or hide will automatically start following you. If you don't want someone to follow you, you can block them at any time.