$thumbprint = 0F273F77B77E8F60A8B5B7AACD032FFECEF4776D

Get-ChildItem -Path Cert:LocalMachineMy | Where-Object {$_.Subject -match "XXXXXXX"}

Thumbprint                                Subject
----------                                -------
0F273F77B77E8F60A8B5B7AACD032FFECEF4776D  CN=XXXXXXX, OU=YYYYYYY

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

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

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