Check your iPad model and current iPadOS version in Settings > General > About
Connect the iPad to Wi-Fi
Plug the iPad into power
Open Settings
Tap General
Tap Software Update
Tap Download and Install if an update is available
Enter your passcode if prompted
Wait for the download to finish
Tap Install Now if prompted
Keep the iPad connected to Wi-Fi and power until the update completes
Restart the iPad if it does not restart automatically
If no update appears, check whether your iPad model supports a newer iPadOS version
If needed, update using a Mac or PC with Finder or iTunes
Back up the iPad before updating if possible