Where do I find IMEI number in iPad?

Only WiFi+Cellular models of iPad have cellular radio hardware - to which the IMEI is an identifier. If you have a WiFi Only model of iPad, there won’t be an IMEI to locate.

To find your IMEI, if applicable, it can be located in iPad settings:

Settings > General > About > IMEI

If you don't have access to your iPad, the IMEI can be located in your AppleID account. Simply sign-in to your AppleID account from any computer using a web-browser:

https://appleid.apple.com

Having signed-in, open the Devices tab. Here you will find an entry for every device associated with your AppleID; tap the related entry to see full technical details of the device - including IMEI/MEID of Cellular devices.

Additional information about finding your IMEI can be found here:

Find the serial number or IMEI on your iPhone, iPad, or iPod touch - Apple Support

Please follow this path,

iPad > Settings > General > About > scroll down and it’ll be listed in a group of settings including Carrier, WiFi Address and modem Firmware. If you long press the number you’ll have an option to copy the number to your clipboard.