As described your battery may require replacement. If the iPad will not power-on at all, even when connected to its Power Adapter, the battery may be dead; the battery must have at least a minimum level of charge to boot the iPad when connected to external Power.
You would be well advised to directly contact Apple Support. You will find the Contact Support link at top-right of this page. Alternatively, you can open a support case using the excellent Apple Support App from another device. If not already installed on your iPad/iPhone, the App can be downloaded from the App Store:
https://apps.apple.com/gb/app/apple-support/id1130498044
As a further alternative, you might visit the Genius Bar at your local Apple Store - where the technicians will be able to test and assess you iPad.