Hi Br Juan Carlos,
As you have only recently enabled the backup and synchronization, you will not receive the "Your backup identity" email.
This is because several months ago, we changed the backup email procedure for new users. In this new procedure, the functionality of the "Your backup identity" email is replaced by the "A new device wants to sync with your Avast Passwords" email. Attempting to synchronize a device will now prompt a "A new device..." email to be sent to the associated email address as part of the synchronization attempt.