If your iPad is nearly 7-8-years old or even older, the battery in that iPad maybe failing or has failed.
Batteries do not last forever.
Time to search online for your nearest, “local” Apple store location and call contact phone numbers and call to make an appointment to have your Apple iPad diagnosed and options presented you.
Failing that,
You need to contact Apple support via the contact support link located at the upper right hand corner of every Webpage of these Apple support communities.
Use the Hardware Repair & Battery usage & Charging support categories.
OR
by installing and using the Apple Support app found in the iOS App Store.
Tap the iOS App Store link below.
https://apps.apple.com/us/app/apple-support/id1130498044
OR
Call contact Apple via the support numbers found in the link bekow.
Contact - How to Contact Us - Apple
Tap the link below.
https://www.apple.com/contact/
Best of Luck to You!