Hi Chun,
As an admin, you should receive "In-App" notifications for all the posts meant to be moderated. When there is a pending item in the moderation section, you see this message on top of your home-page when you log in as an admin or a moderator:

Group moderators can only see the pending items in the moderation section that related to their group(s) only. For example, if you are a moderator of Group A, but there is content from Group B that needs to be moderated, you do not see the item in the moderation section, because you do not have moderation access to group B.
At this moment, Tribe does not send "outside of the app" notifications for the items pending in the moderation panel. For example, you do not receive an email or Slack notification when there is a new item pending in the moderation panel.
We have received this feedback from other customers and well and we will add the external notification for this in the future.