Q: How to restore iCloud backup from one iPad to another one?

You need to be on the iOS Setup Assistant screens to be able to restore to an iCloud backup, so you need to erase all content off the iPad  : Erase all content and settings on your iPhone, iPad, iPod touch, or Apple Watch - Apple Support

On the Setup screens you should then be able to select one of your iCloud backups : Restore your device from an iCloud or iTunes backup - Apple Support

Some things won't be copied from an iCloud restore e.g. audiobooks and tones (they are one-time only downloads), items no longer in your country's store, and your own content (e.g. your own music and videos in the Photos and Videos apps, and photos synced from a computer)