Have no I tunes app. iPad Air 2

Make sure you haven't created a folder with several apps (including iTunes) in it.

Restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

As a final step, try the recovery mode. Turn your device off, then plug it to your computer with the home button pressed. Keep the Home button pressed until you see the iTunes logo on the screen of your iPhone. After that on your computer you should see the iTunes window saying your iPhone needs to be restored to factory settings. Click on the restore button.

More info here: https://support.apple.com/en-us/HT201263

Check to see if it's not hidden via Settings > General > Restrictions > iTunes Store being set 'off' - if it is then turn it back 'on' and it should reappear on a homescreen