Replace text in multiple files in a folder with PowerShell

replFilesFolder.ps1

$filenames = @(get-childitem -Path "<Folder>\*.<Extension>" | % { $_.FullName })

foreach ($file in $filenames) 
{
    $replacementStr = '<Replacement string>' 
    (Get-Content $file) | 
        Foreach-object { $_ -replace '<String to relace>' , $replacementStr   } | 
     Set-Content $file
     Write-Host Processed $file
}