Sharepoint Powershell Form Library - Compare Date, Change Value - sharepoint

Question

I don't have much knowledge of Sharepoint Powershell but I'm attempting to piece something together to automate the checking of expiry date fields inside an infopath form library vs today's date.
I wish to compare every date in the following column,
Construction_x0020_Card_x0020_Expiry
To today's date. If the value is less or is null than today's date (meaning expired licence or no licence) modify the text in the following field:
Construction_x0020_Card_x0020_Type
This is what I have so far;
if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null) {
Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}
$webUrl = "https://####"
$listDisplayName = "HR Employee Record"
$ExpiryDate = #($Construction_x0020_Card_x0020_Expiry)
?? Not sure if this works,$Construction_x0020_Card_x0020_Expiry is an array?
$TodayDate = (Get-Date).ToString("dd-MM-yyyy")
$convertedExpiryDate = $ExpiryDate.ToString("dd-MM-yyyy")
?? Not sure if this works, $Construction_x0020_Card_x0020_Expiry is System.Object[] trying to convert to System.DateTime
foreach ($item in $convertedExpiryDate.items | where {$convertedExpiryDate -lt $TodayDate}) {
if ($convertedExpiryDate -eq $null) {
Write-Host #($Construction_x0020_Card_x0020_Type)["$null"]
} elseif ($convertedExpiryDate -lt $TodayDate) {
Write-Host #($Construction_x0020_Card_x0020_Type)["Expired"]
} elseif ($convertedExpiryDate -ge $TodayDate) {
Write-Host #($Construction_x0020_Card_x0020_Type)["Valid"]
}
}
Thanks,
Lance