iPad3 - or iPad Air3, as suggested by the tags appended to your post?
In reverse order, an iPad Air3 can be updated to the current version of iPadOS - at time of writing, this being iPadOS 13.7. The iPad Air3 is also compatible with the soon to be released iPadOS14.
By contrast, iPad3 cannot be updated beyond iOS 9.3.5 (WiFi Only models) or iOS 9.3.6 (WiFi & Cellular).
Apple ended update support for iPad3 in September 2016. iPad3 cannot be updated to iOS 10 or later versions, as the internal hardware does not meet the minimum technical requirements for new versions of iOS/iPadOS. The 32-bit hardware upon which it is based is effectively obsolete. More recent versions of iOS/iPadOS are designed for 64-bit devices.
Many App Developers have also dropped support for older devices and iOS versions preceding iOS11/12/13 - and have withdrawn older versions of their Apps from the Apple App Store, now limiting utility and usefulness of older devices.
If Apps that you need to use now have higher minimum iOS-version requirements, your only option is to replace your iPad with newer model. Of current models, even the entry-level iPad7 model supports current iPadOS 13/14 - and has hardware specifications and capabilities that vastly outperform an iPad3.
I hope this information is helpful - if only in clearly stating the contrasting capabilities and limitations of iPad3 versus the iPad Air3.
