You can find your serial number in 4 places.  The serial number is alpha numeric in the following format xxxx-xxxxxxxxx-xxxxxx.

1) If you've connected your device to your home network, you can find the serial number in your mobile app.  Navigate to Settings>Technical Info.

2) Printed on the white sticker found on the bottom of the device.  

3) On the device menu. 

• Press and hold your thumb on the device screen for 8-12 seconds until an alternative menu appears
• Swipe left once and the serial number will appear

4) On the outside of the shipping carton your device came in.