Determining the installed PowerShell version on your machine is pretty straightforward. Though there is a few gotcha's so let's go over how to get your currently installed PowerShell version.
$PSVersionTable.PSVersion to determine the engine version. If the variable does not exist, you can assume the installed version of PowerShell is version
PS C:\> $PSVersionTable.PSVersion Major Minor Build Revision ----- ----- ----- -------- 4 0 -1 -1