Just purchased my third iPad, went to play music this morning. There is no music on it, why?

Learning how to use your iPad.

Maybe you need all of this to help you properly learn to use and navigate iOS 11.

iPad User Guide for iOS 11 by Apple Inc.

https://itunes.apple.com/us/book/ipad-user-guide-for-ios-11/id1263310093?mt=11

Another very good iOS 11 Users Guide

https://arstechnica.com/gadgets/2017/09/ios-11-thoroughly-reviewed/

VIDEOS!!

iOS 11 Basics

https://www.youtube.com/watch?v=cnEfNBQ_F1Q&list=WL&index=81&t=904s

https://www.youtube.com/watch?v=_rgnwfgHXSg

iOS 11 Dock

https://www.youtube.com/watch?v=i2eXus8fweg

https://www.youtube.com/watch?v=MBoeJCmxnpA

iOS 11 Multitasking

https://www.youtube.com/watch?v=JsAh2EjyIVo&index=83&list=WL&t=8s

ITunes Support

https://support.apple.com/itunes

Good Luck to You!

What has been done with the iPad since the music was in its Music app ?

Did you put music on it? They don't come with music preloaded.

Is that music purchased from the iTunes store? If not then that's expected behavior for iOS devices as it's not included in backups. Mostly due to copyright restrictions.