Hi, @golden alick
Thank you for posting in Microsoft Q&A forum.
You may use the default report Count of Configuration Manager clients by client versions in the report folder Site - Client Information.
It's recommend to use Automatic Client Upgrade, this is the most efficient method for large environments. You can configure the site to automatically upgrade clients to the latest Configuration Manager version. When Configuration Manager identifies an assigned client's version is earlier than the hierarchy version, it automatically upgrades the client. You can find more details on how to configure this here.
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Add comment".
After the way you tag questions on Q&A is updated, for any "Microsoft Configuration Manager" related problem, you can tag it with "Microsoft Intune", and then "Microsoft Configuration Manager" as the child tag.