To find the serial number on your phone, dial *#60#, check on the Settings menu or look for the printed number somewhere on the body of the phone. Many smart phones allow you to use all three of these methods.
When dialing *#06#, do so as if making a regular phone call, and the serial number pops up on the screen. Alternatively, go to the Settings menu on your phone and click on any link that provides general information about the phone to search for the number. If the phone is dead, search for the number printed on the body of the phone, on a sticker or inside the battery case.