iPad not turning off automatically

An iPad will only automatically shut-down if the battery is nearly discharged. However, the iPad will automatically lock and enter its low power "standby" state when it is idle. The period the the iPad will remain awake and unlocked is controlled by its Auto-Lock setting:

Settings > Display & Brightness > Auto-Lock > set as preferred

Be aware that selecting Never is not recommended - as the iPad will remain unlocked. Anyone that has physical access to an unlocked iPad can access everything saved on the iPad.

You are very welcome.

As a newcomer to iPad and iPadOS, in addition to these ASC forums where you are always welcome to ask questions and seek help, there are many useful sources of information and guidance...

The iPad User Guide is a rich source of frequently overlooked information. The Guide for your iPad is available online using a web browser (such as Safari):

iPad User Guide - Apple Support

The Tips App, installed by default on all new models of iPad, provides a brief introduction - and leads you to the online User Guide. In case you missed it - or if the App needs to be reinstalled - here is a link to the Tips App:

https://apps.apple.com/gb/app/tips/id1069509450

Apple also has a huge YouTube Channel - containing videos and feature guidance:

https://www.youtube.com/user/Apple