When you install new PowerShell modules via Install-Module, PowerShell remembers the install location. So it is easy to get a list of modules you installed via Install-Module:

PS> Get-InstalledModule

Version Name                       Repository Description                                               
------- ----                       ---------- -----------                                       ISESteroids                PSGallery  Extension for PowerShell ISE 3.0 and better               
2.2.0   PoSHue                     PSGallery  Script and Control your Philips Hue Bridge, Lights, Gro...
0.14.0  platyPS                    PSGallery  Generate PowerShell External Help files from Markdown     
2.4     PSOneTools                 PSGallery  commands taken from articles published at https://power...
1.0     QRCodeGenerator            PSGallery  Automatically creates QR codes as PNG images for person...
1.0     ScriptBlockLoggingAnalyzer PSGallery  Functions to manage PowerShell script block logging       
1.0     UserProfile                PSGallery  This module manages user profiles on local and remote c... 

Since newer versions are installed side-by-side, it may be worthwhile to search for older versions that are no longer needed:

Get-InstalledModule |
Get-InstalledModule -AllVersions 

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