Do I need to delete everything on my old iPad after setting up the new iPad

Have you already transferred all data using one of the methods listed here:--> Transfer data from your previous iOS or iPadOS device to your new iPhone, iPad, or iPod touch - Apple Support ?

Once you're sure that the process was successful, you can decide to delete you all your info from the old device, performing these instructions:--> What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Regards

Giulio

No, you don’t need to erase your old iPad - unless you intend to give it away or otherwise dispose of it.

Can you describe the issue that you see with the new iPad? If the process has stalled for a considerable period, a forced-restart may resolve the problem - or allow the process to complete.

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

Note:  If iPad still doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won’t turn on or is frozen. Or if your iPad isn’t working correctly after you restart it, see the iPad Support website.

No. You only need to erase the old iPad if you plan on giving it away or selling it.

Otherwise, once the old iPad indicates the transfer is complete its done.

What does the new iPad show on screen exactly?