Get thumbprint of a certificate

You can use Select-Object to get only the Thumbprint-property:

Get-ChildItem -Path Cert:\LocalMachine\My | 
    Where-Object {$_.Subject -match "XXXXXXX"} | 
    Select-Object -ExpandProperty Thumbprint

All you have to do is wrap the command in parentheses, and then use dot-notation to access the Thumbprint property.

Try this out:

$Thumbprint = (Get-ChildItem -Path Cert:\LocalMachine\My | Where-Object {$_.Subject -match "XXXXXXX"}).Thumbprint;
Write-Host -Object "My thumbprint is: $Thumbprint";

If you get multiple certificates back from your command, then you'll have to concatenate the thumbprints into a single string, perhaps by using the -join PowerShell operator.

$Thumbprint = (Get-ChildItem -Path Cert:\LocalMachine\My | Where-Object {$_.Subject -match "XXXXXXX"}).Thumbprint -join ';';
Write-Host -Object "My thumbprints are: $Thumbprint";