You're GRADUATING. Congratulations!
Keep in mind there are two ceremonies you could attend - the Colleges of Letters, Arts, & Science convocation, and the University of Arizona commencement. For information on the University of Arizona commencement, please see the commencement website.
For both ceremonies, you may want to wear commencement robes, tassels, or sashes. All information regarding regalia can be found at the UA Bookstore.