Powershell - add leading zeros in CSV File - powershell

Question

I built a powershell script in order to format the content of a csv file. It is working fine for the majority of columns except for one column named "Kunde_PLZ"
I want to add leading zeros to the content of that column "Kunde_PLZ" if the number inside the column is shorter than 4 digits. Trying to use padLeft(5,"0") for that.
Import-Csv "c:\temp1.csv" -Delimiter ";" |
% {$_.BESTELLEINGANG = ([datetime]($_.BESTELLEINGANG)).ToString('dd.MM.yyyy');$_.LIEFERDATUM = ([datetime]($_.LIEFERDATUM)).ToString('dd.MM.yyyy');
$_.KUNDENNUMMER =($_.KUNDENNUMMER) -replace '\.', '';$_.KUNDENNUMMER =($_.KUNDENNUMMER) -replace ',.*', '';$_.KUNDE_PLZ = $_.KUNDE_PLZ.padLeft(5,"0") ;$_} |
sort Kundennummer -Descending | Select * -ExcludeProperty "KUNDE_ZUSATZ" |
Export-Csv "c:\resultfile.csv" -Delimiter ";" -Encoding UTF8 -notypeinfo -Force
But no leading zeros are added in the resultfile for the column "KUNDE_PLZ".
I also tried using foreach , but still no leading zeros added
$file = Import-Csv "C:\temp1.csv" -Delimiter ";" |
% {$_.BESTELLEINGANG = ([datetime]($_.BESTELLEINGANG)).ToString('dd.MM.yyyy');$_.LIEFERDATUM = ([datetime]($_.LIEFERDATUM)).ToString('dd.MM.yyyy');
$_.KUNDENNUMMER =($_.KUNDENNUMMER) -replace '\.', '';$_.KUNDENNUMMER =($_.KUNDENNUMMER) -replace ',.*', '';$_} |
sort Kundennummer -Descending | Select * -ExcludeProperty "KUNDE_ZUSATZ"
$file | foreach{$_.KUNDE_PLZ = $_.KUNDE_PLZ.padLeft(5,"0") }
$file | Export-Csv "C:\resultfile.csv" -Delimiter ";" -Encoding UTF8 -notypeinfo -Force
Any ideas how to get the leading zeros added to the column "Kunde_PLZ" inside the csv file ?