Powershell: Add a linebreak in the find and replace strings

I want to add data to a xml export file. Therefor I need to search for a multiple occurrences of the value with has a linebreak (otherwise the string is not unique for the value I want to change) and replace the value with another linebreak.

There are multiple files in the directory with a filename which contains the date and time on which the file was generated.

The code does work on values without linebreak. I tried with the 'n as linebreak or with Here-String (searched google), but with no success.

My code so far:

# location .xml files
$files = Get-ChildItem D:\test\*.xml
# value to search for
$find = "<waarde/></telefoonNrWerk>"
# and replace the value with
$replace = "<waarde>onbekend<waarde/></telefoonNrWerk>"
# command to do the work
Foreach ($xmlfile in $files)
	{
	(Get-Content $xmlfile.Name) | Foreach-Object {$_ -replace $find, $replace} | Set-Content $xmlfile.Name
	}