I am able to get the date of the last modified item in the list using the script below:
$SiteURL="https://abc.sharepoint.com/sites/sitename"
$ListName="Documents"
Connect-PnPOnline -Url $SiteURL -Credentials (Get Credentials)
(Get-PnPList -Identity $ListName).LastItemUserModifiedDate
Please help me with getting the Item ID of the above last modified item.