I’m not able to activate my iPad after using find my ipad

Did you put it in the lost Mode? What happens when you try? Error message(s)? More information would help.

From the article below.

Turn off Lost Mode on an iPhone, iPad, iPod touch or Apple Watch

When you find your lost device, do either of the following to turn off Lost Mode:

• Enter your passcode on the device.
• In Find My iPhone on iCloud.com, click All Devices, then select the device that is in Lost Mode. Click Lost Mode, click Stop Lost Mode, then click Stop Lost Mode again.

Note: If you had any cards suspended when you put your device in Lost Mode (credit or debit cards for Apple Pay, or student ID cards or Express Transit cards), when you turn off Lost Mode and sign back in to iCloud, you can use them again.

Find My Phone - Lock and track your device using Lost Mode