i don't remember my old icloud email or password. what do I do?

My ipod 5 has the restore thing on the screen where it wants you to plug it into itunes. I searched how to do that and the last step is to enter your apple ID which is my old icloud email address. I completely forget it because its been about 4 years since I've gotten on the ipod, but when I tried it had the restore screen up. I don't know what to do.