Links to Relevant Wiki Articles(s):
You can resend a confirmation email under Account Settings > Email. There you could change the email address associated with your Scratch account and/or verify its spelling, in case of a typo.
It may take awhile for the email to arrive. Please check your Spam folder, just in case the email was sent there.
If your email address is a student email (many student email addresses end in ".edu"), you may not be able to receive emails from Scratch. If this is the case, we can confirm your email if you send us a message. Please note that the Scratch Team will not confirm excessive numbers of usernames. In those cases, you should use an email address that will allow you to receive messages from the Scratch Team.