Trying to change my iPads password from my phone

Not possible. The screen unlock passcode can only be changed on the device itself.

The passcode is the encryption (and decryption) key for the contents of the iPad.

If you don’t know the passcode, the protected data is inaccessible.

You’ll have to reset the iPad.

If you forgot the passcode on your iPad, or your iPad is disabled - Apple Support

If you have a backup of your iPad, you can then restore it.