Win 8.1 reinstall
Windows PowerShell comes installed by default in every Windows, starting with Windows 7 SP1 and Windows Server 2008 R2 SP1. If you are interested in PowerShell 6 and later, you need to install PowerShell Core instead of Windows PowerShell. For that, see Installing PowerShell Core on Windows. Finding PowerShell in Windows 10, 8.1, 8.0, and 7