On an iPad:
You can find it on the back of the device
You can also find it by taking the following steps
Go to “Settings”
Go to “General”
Go to “About”
You will see it near the top of the page
On a Samsung Tablet:
Go to “Settings”
Scroll down and press “About Tablet”
You will see it near the top of the page
On Microsoft Tablet:
Select “Start”
Click on “Settings”
Click on “System”
Click on “About”
Find “Windows Specifications”, and look for your Serial Number
Other possible ways to find your serial number on a Microsoft Tablet:
“About” > “Model & Hardware” > Serial Number
Under the keyboard (if applicable)
Flip out the kickstand (if applicable), look for numbers near its base
Once you find the serial number:
Type the serial number into the "Add item" information form in your account.
When you take a photo of the "About page"
Take a clear photo showing the entire screen of your tablet with the about page showing
Then take a photo of the back/bottom of your tablet