Whether you are able to update your iPad to a newer version of iOS/iPadOS will be dictated by your iPad model - and the currently installed version of iOS. You can find this information here:
Settings > General > About
Not sure which iPad you have? Identify your iPad model.
Here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:
iPad1 - iOS 5.1.1
iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi & Cellular)
iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi & Cellular)
iPad Air1, iPad mini2 and iPad mini3 - iOS 12.4.8
Newer models, not appearing in this list, are all able to be updated to the current version, iPadOS 14.1.
The tags appended to your post suggest that your have an iPad4...
Update support for you iPad4 ended September 2017. The final iOS releases for this model were iOS 10.3.3 (WiFi Only models) and iOS 10.3.4 (WiFi & Cellular).
iPad4 cannot be updated to any later major version of iOS as it lacks hardware needed to run more recent versions. The 32-bit platform upon which the iPad4 is based is technically obsolete; newer versions of the Operating System are designed to run on 64-bit system architecture and CPU hardware - that the iPad4 doesn’t have. It’s not possible to run 64-bit code on a 32-bit system.
Most App Developers have since dropped support for 32-bit devices (i.e., iOS versions preceding iOS11/12/13) - and have withdrawn older versions of their Apps from the Apple App Store. Withdrawal of Apps supporting older models of iPad is making their utility and usefulness significantly more limited. Once compatible versions Apps are withdrawn, you’ll not be able (re)download or (re)install them.
If Apps that you need to use now have higher minimum iOS-version requirements than your iPad is able to support, your only option is to replace your iPad with newer model. Of current models, even the budget-conscious iPad8 supports current iPadOS14 - and has hardware specifications and capabilities that vastly outperform the very old iPad4.
I hope this explanation proves to be helpful - if only in clearly stating the potential limitations of your current iPad - and your available options.
