Ipad 9-th Generation

From settings:

Settings > Home Screen & Dock > Show Suggested & Recent Apps in Dock - set to OFF

If you have disabled the setting, but your iPad is still showing Recently Used Apps in the dock, try a forced-restart - as this will usually resolve an isolated software issue:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.