how to update version before set up of ipad

You must set up the iPad, then update the iOS version, then restore the iPad to factory settings, if you need to use a Backup to set it up.

Alternatively You can connect the iPad to a computer before setting it up, and use iTunes or Finder to restore and update the iPad before setting it up.

Click here ➡️ Restore an iPhone, iPad, or iPod touch that needs a newer version of iOS or iPadOS - Apple Support