Your 2012 iPad 3rd generation has not been supported by ANY major upgrades/uodates Apple in over 4 years and third party iOS app developers have, largely, dropped/endee/discontinued app support for all 8 and 9-year old iOS devices that are stuck with iOS 10, iOS 9 and earlier.
There are no more older, compatible apps, for initial download, from the iOS App Store any longer, making these old 8, 9 and 10-year old iPad models, pretty much obsolete and useless, now!
Since this iPad is basically completely unsupported now, you could try searching the Internet for a competent, third party Apple device repair center capable of replacing batteries in older Apple mobile devices.
Be aware, if this old iPad is already dead and has never been backed up to Apple iCloud or other online, offsite data storage/backup services, like Google Drive/DropBox, Box, Amazon Cloud services, Flickr (for photos/images amd videos ) or to iTunes on a Windows PC or older Mac or using the Finder on newer Macs with newer macOS versions, then everything on that iPad is already gone.
Sorry, this Pad is too old, now.
If you need/want a usable iPad with current iOS/iPadOS with current, updated apps, then you really need to forget about this very old iPad and need to seriously consider a new iPad model OR a much, MUCH “newer” , used iPad model capable of running the latest iPadOS versions.
There are plenty of newer, older iPad models that can run the current versions of iPadOS 14.
A lot has happened with iPad and iOS in almost 9-years since the 2012 iPad 3 was introduced.
Sorry & Best of Luck to You!