PowerShell 6.x is not a Microsoft program. PowerShell 7 is not the default version of PowerShell and cannot replace PS 5.1
I recommend that you start by learning both PowerShell and Computer technology. Don't get caught up in numbers that you have no understanding of. They are not helpful before you learn computer technology.
I will leave you with this - Microsoft has confused the issue by making it sound like PS 7 is an upgrade to previous versions of PS. It isn't. It is a cross platform program that allows development of scripts that work on many platforms but cannot
yet replace PowerShell.
Once you learn basic computer science and technology all of this will become more understandable.
\_(ツ)_/