can i trade in my ipad 9th generation

You can verify eligibility for trade-in and obtain an estimate of the potential trade-in value here:

Apple Trade In - Apple

In addition to an online trade-in, you can also trade-in at a physical Apple Store - many choosing this option by preference as the device(s) can be checked, the trade-in value finalised and the process completed while in-store. Be aware that Apple’s in-store trade-in values may differ from the online estimate.

Before parting with your iPad, whether trading-in or selling privately, ensure that the device is properly prepared:

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

you can trade in all of them minus the latest model of each device type

you can read more about it here

Apple Trade In - Apple