Forget this iPad!
It is not worth anything and even if a third party battery could be installed by an competent third party repair center competent enough to do a battery replacement in that iPad, it will cost more than tbat old iPad is worth, which is basically nothing.
Also, during an actual battery replacement, there is ALWAYS the possibility of complete data loss.
If that happens, there is no way, NOOOO WAY to recover anything from that old device as Apple AND ALL third party app developers stopped supporting this ancient iPad by 2015.
NO SUPPORT! NO APPS! NOTHING!
This is an over 11-year old iPad, today!
It's 2021, now.
Time to move into the present and with a much, MUCH newer of new iPad model.
A WHOLE LOT has happen with iPad and iOS ( now iPadOS ) in the past 6-11-years since that iPad model was introduced.
Time you really need to seriously consider a purchase of a new iPad model OR a much, MUCH “newer” and less expensive, refurbished or used iPad models, from better known, trusted sources, like other Apple product/device retailers/resellers, some locally or from online, 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.
If you need OR ONLY able to purchase older, less expensive iPad models, look at older IPads from 2014 and later.
All of these older model iPads below CAN run the latest iPadOS versions and the up and coming iPadOS 15.
2014, 9,7 inch screen iPad Air 2 models
2015, 7.9 inch screen iPad Mini 4 models
2015-2017, 12.9 inch screen iPad Pro models. ( 1st gen Pencil support )
2016, 9.7 inch screen iPad Pro models ( 1st gen Pencil support )
2017, 10.5 inch screen iPad Pro models ( 1st gen Pencil support )
2017, 9.7 inch screen iPad 5th gen models
2018, 9.7 inch screen iPad 6th gen models ( 1st gen Pencil support )
2019, 10.2 inch screen iPad 7th gen models ( 1st gen Pencil support )
2020, 10.2 inch screen iPad 8th gen models. ( 1st gen Pencil support )
Get the largest internal data storage model you can afford as NO Apple iOS device has expandable storage.
I am sorry that you had to learn all of this, but this does not change any of the facts regarding these older iOS devices.
Sorry & Best of Luck to You!