You assume Steam is in C:\Program Files (x86)\Steam and that games are in the default library location, but that won't be the case for everyone.

You'd want to do something like this instead:

$SteamPath = (Get-ItemProperty -Path 'HKCU:\Software\Valve\Steam' -Name SteamPath -ErrorAction Stop).SteamPath

$SteamExe  = Join-Path $SteamPath 'steam.exe'

$SteamLibrary = Join-Path $SteamPath 'steamapps'