How Do I Find The iPad Serial Number And Identifier (UDID)?
You can find this info in iTunes even if your iPad isn't connected to your Mac.
If your iPad is connected to your Mac: launch iTunes, select your iPad, and click the Summary tab. The serial number will be listed next to other info about your iPad. You can click on the serial number to make the UDID appear.
If your iPad is not connected: launch iTunes, go to iTunes->Preferences (Command+Comma) and click on the Devices tab. Your iPad backup will be listed. Hold your cursor over the iPad and the serial number, etc. will appear.