Why is my Set-DisplayResolution command in Powershell missing?

I'm using Parallels on my Mac to run the Windows 8.1 operating system. Parallels has a quirk that resets the screen resolution to the highest level every time it is restarted. Thus, I'd like to write a short powershell script that will automatically sets my screen resolution to the one I prefer. The problem is, using either the Set-ScreenResolution or the Set-DisplayResolution gives me the following error:

Set-DisplayResolution : The term 'Set-DisplayResolution' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again. At line:1 char:1 + Set-DisplayResolution + ~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : ObjectNotFound: (Set-DisplayResolution:String) [], CommandNotFoundException + FullyQualifiedErrorId : CommandNotFoundException

Any idea why this is happening?

I'm using Windows 8.1 64 bit. The version of my Powershell is 4.0. I'm using Parallels 9 as my virtual machine on the Yosemite operating system (mac).