For older models of iPad that don't have the battery health feature, such as your iPad9, there are software packages available that can access battery cycle count. Popular choices for Mac are Coconut Battery and iMazing - whereas iMazing is available for PC.
https://www.coconut-flavour.com/coconutbattery/
The are also third-party shortcut scripts available that can semi-automate analysis of your iPad's analytics files - and provide a calculated estimate based upon the charge-cycle count. If this method is of interest, try using a Google search for "iPad battery health shortcut".
If you are experiencing difficulties with your iPad battery holding charge, you might be best advised to have your iPad tested. If you directly contact Apple Support - and explain your problem - you can request a remote battery diagnostic. The tests will confirm the status of your battery - and other elements of your iPad’s health.
Alternatively, a visit to the Genius Bar at your local Apple Store would provide opportunity for your iPad to be similarly tested by the Apple technicians - after which you can explore your available options.
Genius Bar Reservation and Apple Support Options - Apple
You can contact Apple Support using the Contact Support link at top-right of this page. You can also initiate a support case 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
Rechargeable batteries are a consumable item that will slowly decline over time - every recharge reducing the total battery capacity by a tiny amount. This effect is cumulative; eventually, the battery will need to be replaced.
"Battery health" is influenced by many factors.
An iPad's battery is rated to retain at least 80% of its original capacity after 1000 full charge cycles - one full cycle being any combination of charging that together sums to 100% (e.g. 50 + 25 + 15 + 10 = 100 = 1 cycle). Simple arithmetic would therefore suggest that battery health will decline at about 1% for each 50 charge cycles - but this alone does not take into account that the rate of decline is non-linear.
Other factors can influence overall battery health. High ambient temperatures can permanently reduce the battery's ability to retain full charge - as can maintaining the battery at 100% charge for very long periods of time that leads to chemical aging of the battery. Limiting the battery charge to ~80% of maximum is intended to reduce the chemical aging effect. That said, independent studies have demonstrated that restricting charging to only 80% of maximum has little if any impact upon the overall longevity of the iPad's battery.