Create Folder using powershell

I am using below script which create csv files in batches ex:Batch1,Batch2, but how should modify this script so it will create create folder and insert all batch files inside that.

Tried this but not working

 $BatchNr = 1
    Import-Csv -Path .\Master.csv |Create-Batch -Size 50 |ForEach-Object {
        $_ |ForEach-Object {
            $_ # do something with each item in the batch of 50
        } $files  | Export-Csv ".\Batch$BatchNr.csv"
     
    ForEach ($file in $files)
  {
    $folder = New-Item -type directory -name $file.BaseName;
    Move-Item $file.FullName $folder.FullName;
  }
        $BatchNr++
    }