Tesserax is correct.
Versions of Pages, Numbers and Keynote maybe no longer available for your iPad and for your version of iOS.
These require iOS 12, now.
Your iPad Air is too far behind in iOS upgrades/updates.
Depending on which iPad Air you have a 2013, 1st gen iPad Air can be upgraded to iOS 12.4.x.
A 2014 iPad Air 2 can be upgraded to iPadOS 13.3, currently.
You can upgrade that iPad Air to iOS 12.4.x/iPadOS 13, but you will need to connect that iPad Air to a computer, connected to the Internet, running the latest version of iTunes and do the iOS/iPadOS upgrade of your iPad Air through iTunes on a computer.
Best of Luck to You!