Hi @walid issa , you could try something like this:
$startDate = (Get-Date).AddMonths(-3)
$guestUsers = Get-AzureADUser -Filter "UserType eq 'Guest' and WhenCreated -ge $startDate"
Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James