Doing trade in. Forgot to turn off Find My Ipad

See:

What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

If you no longer have your iPhone or iPad

If the steps above weren’t completed and you no longer have your device, follow these steps:

1. Ask the new owner to erase all content and settings using the above steps.
2. If you're using iCloud and Find My [device] on the device, sign in to iCloud.com/find or the Find My app on another device, select the device and click Erase. After the device has been erased, click Remove from Account.
3. If you can’t follow either of the above steps, change your Apple ID password. This won’t remove personal information that’s stored on your old device, but it prevents the new owner from deleting your information from iCloud.
4. If you’re switching to a non-Apple phone, deregister iMessage.
5. If you're using Apple Pay, you can remove your credit or debit cards at iCloud.com. Choose Account Settings to see which devices are using Apple Pay, then click the device. Next to Apple Pay, click Remove.
6. Remove your old device from your list of trusted devices.
7. If you’ve purchased an AppleCare plan for your device, cancel your AppleCare plan.

Yes

if find my is active they will send you an email telling you to turn it off.

If you don’t, they will return the iPad to you.