How did you try to copy it onto your iPad?
Once its been ripped onto your iTunes library on your computer you can then sync it to the iPad. See here: link-> Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support
Another option is, if you are subscribed to Apple Music and have the iCloud Music library option turned on, then you have to wait for it to scan your library and match or upload the tracks and they'll appear on your other devices. Details here: link-> Turn on Sync Library with Apple Music - Apple Support