You can find your old friends on Facebook if they have subscribed for Facebook accounts using their email addresses that you already have. You can also use the social circles such as a school or college that you attended; most probably you will recognize the users in that group.
I graduated with 593 in my class alone, so I know how you feel. I was able to start with just my graduating year and started scrolling, then it would spark a memory of a name to look for. Also search by former employer. Once you start getting a few friends on there, you can look through their friend lists for people and Facebook will provide suggestions as well.