trying to restore Ipad

Did you restore the iPad by connecting it in Recovery Mode to your Mac, aas explained in this article?

If you forgot your iPad passcode - Apple Support

Are you using the Apple USB cable, that came with the iPad, to connect to your iPad to the Mac?

Is the iOS download onto the Mac is corrupt, or do you get the message after downloading the iOS software, during the process of installing it on the iPad?

If you are getting this message during the restore process from the backup, the backup data has been damaged.

In that case try to set up the phone "As a new device", filling in your personal data manually.

That way you will at least have a working iPad. And if you happen to have an iCloud backup, you could use the iCloud backup to restore from.

In case you are getting this message during the transfer of the downloaded iOS software to the iPad, this looks like a hardware issue.

The computer downloads the iOS software first and then checks is for damage. If the downloaded iOS software is marked as damaged by your computer, you could delete the software package and start again.

You should get the option to either download the software first and install it in a second step after verifying the download, or download and install in one step.

Choose to download and verify, to make sure this is not the reason for the error message.