Get-ThumbprintFromCertFile.ps1

function Get-ThumbprintFromCertFile {
    param (
        [Parameter(Mandatory)]
        [ValidateScript({Test-Path $_})]
        [ValidatePattern(".*\.cer")]
        [String]$CertificatePath
    )
    
    $CertificatePath = (Get-Item $CertificatePath).FullName
    try {
        $certObj = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Certificate2 `
            -ArgumentList "$CertificatePath"
    }
    catch {
        throw "Could not load Certificate"
    }
    return $certObj.Thumbprint
}