An iPad battery is rated to maintain at least 80% of its initial capacity after 1000 full charge/discharge cycles - whereas an iPhone is rated to have 80% of initial capacity after 500 full cycles.
All rechargeable batteries have a finite service - and at some point will require replacement. With every full recharge cycle, the overall battery capacity will be reduced by a tiny amount, this being cumulative. Ever so slowly, the battery will lose performance, both in its maximum usable capacity - and its ability to supply peak power demands in some circumstances.
Unlike iOS for iPhone, iOS/iPadOS for iPad has never had the Battery Health feature - most likely because iPad batteries are both considerably larger and have a much longer service life - their are third-party software packages available that can access battery cycle count. Popular choices for Mac are Coconut Battery and iMazing - whereas iMazing is available for Windows PC.
https://www.coconut-flavour.com/coconutbattery/
https://imazing.com/
If you have any concerns for your battery capacity, you might directly contact Apple Support and request a remote diagnostic test. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively and perhaps easier, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad:
Genius Bar Reservation and Apple Support Options - Apple
