Updating Problems With Ipad 3rd generation

You cannot update your iPad further than iOS 9.3.5. It is not capable of running the newer 64 bit architecture iOS levels. If you need the newer iOS levels, then you need a newer iPad.

A 7-year old iPad 3rd generation cannot upgrade/update beyond iOS 9.3.5.

Its internal hardware is too old underpowered and now incompatible with any current and future versions of iOS.

If you need/want to use tge latest iOS versions with the most up to date apps, it looks like it is time to purchase a new iPad from Apple or a discounted, refurbished iPad from Apple's Refurbished & Clearance section of Apple’s Website.

Best of Luck to You!