Like your serial code for the game?
It's listed on the accounts page under payments if you purchased the game from ZOS, if you got it from another retailer you need to contact them to find out where it is.
If it's something else then please explain. You might also want to post in Customer Support - English in future because it's more likely to be noticed by ZOS help teams.
@Turelus - EU PC Megaserver "Don't count on others for help. In the end each of us is in this alone. The survivors are those who know how to look out for themselves."