How can I check the battery health of my iPad 5th Generation?

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. 

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.

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/

https://imazing.com/

There is no Battery Health meter on iPad, like there is on iPhone.

You can certainly look in the App Store for a 3rd party app, which might provide such a reading.

All batteries degrade with use - or, more precisely, they lose capacity by a tiny amount for every recharge cycle. Eventually, all rechargeable batteries will need to be replaced.

iPad batteries are rated to retain at least 80% of their original “as new” capacity after 1000 full charge cycles - a full cycle being any combination of charging that combined amounts to 100% (e.g., 50% + 20% + 15% + 10% + 5% = 100% = 1 full recharge cycle).

Given the cost of battery replacement, for an older model iPad with an older CPU, it may not be cost-effective to replace the battery. In such circumstances the cost of battery replacement might be better spent against a newer model that has a more recent (and more powerful) CPU and more RAM - both significantly contributing to improved performance and capabilities.