Using the HMI display (VW3A1101), you can find the serial number for the drive in the Identification Menu, 1.11. The path is Drive Menu > 1.11 Identification. The 6th line from the top in this menu shows the drive serial number. (The line after MC Software).
You can also find the serial number on the nameplate. The nameplate is a sticker on the right side of the drive itself. the serial number is located under the bar code and will begin with EL, 88, 8B or 6W.