Expanding upon sberman's concise description...
There is a known issue with some new (unused) devices - where the automatic update to the current version of iPadOS may stall while transferring data from an existing device. If encountered, the fix is straightforward; you simply need to interrupt the stalled update process with a forced-restart:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.

After restarting the iPad, allow the new iPad to complete initial setup and software update without attempting to transfer data from the old iPad - setting-up using your AppleID (now known as your Apple Account).
When the update process has completed, reset the iPad - and THEN perform the QuickStart transfer:
Settings > General > Transfer or Reset iPad > Erase All Content & Settings
As an alternative to QuickStart, you might instead consider restoring an iCloud or iTunes backup of your old iPad to your freshly updated new iPad:
https://support.apple.com/118105