I did the whole quest chain and go to Korin's Tower but when I get there he has no quest for me. I am level 30. What do I do?

I don't know if this applies for the Adult Quest, but outside of Korin's Tower on the bridge is a brown super box, kill it and get the red ticket, then right click that red ticket to activate the quest, then simply follow the quest ...

If you mean the red ticket that activates the quest I used that already
Im Inside of Korin's tower but he wont talk to me to change my class or change me to an adult. I dont know what to do from there.

Look for Master Class guide on forum

nvm I retraced my steps and picked the quest up, the indian dude decided he had enough fun keeping quiet and gave me the quest