How do I turn off auto-sleep mode on iPad?

This the setting that you will need to change:

Settings > Display & Brightness >

• Auto-Lock > select Never

If you have a folio cover that can automatically lock your iPad, you may wish to ensure that the associated Lock/Unlock setting remains enabled.

• Lock/Unlock - set to ON

Aside from implications for battery endurance before recharge will be necessary, you should note that disabling auto-lock has a potentially unwanted side-effect for device security - in that the iPad will not automatically lock to prevent unauthorised access to your iPad. As such, anyone will be able to access your iPad unless you have manually locked the screen.

If your iPad is not in Low Power Mode

Go to Settings > Displays and Brightness and select Auto-lock and select never.

Note: this will decrease your iPad battery significantly.