$username = "amos@contoso.onmicrosoft.com"
$password = "Password"
$cred = New-Object -TypeName System.Management.Automation.PSCredential -argumentlist $userName, $(convertto-securestring $Password -asplaintext -force)
$Url = "https://contoso.sharepoint.com/sites/dev"
Connect-PnPOnline -Url $Url -Credentials $cred
$ctx = Get-PnPContext
$authenticationCookies = $ctx.credentials.GetAuthenticationCookie($Url)
Write-Host $authenticationCookies