Your iPad is too old for any more iOS upgrades/updates.
Your iPad is 10-year old now.
Sorry.
Apple ended support for all 8-10-year old iOS devices well over 4 years, ago, in 2016.
Third party app developers abandoned and stopped supporting these 8-10-year old iOS devices nearly 3 years, ago, in 2018.
There are, virtually, NO MORE third party apps available from the iOS App Store, any longer!
Third party compatible apps for such old devices are few and far between, now, in 2021.
Sorry.
If you need/want an iPad with an up to date iPadOS with access to current, updated apps, then you really need to seriously consider a new iPad model OR a much, MUCH “newer” and less expensive, refurbished or used iPad models, from better known, trusted Apple product/device retailers/resellers, locally or from on the Web/Internet capable of running the latest iPadOS versions. There are PLENTY of newer, older iPad models that can run the latest, current versions of iPadOS.
Sorry & Best of Luck to You!