My data structure looks like this:

I want to be able to access every users listings to make an array of all listings however I do not know every users ID or Listing ID so i can not do:
Database.database().reference.child("users").child(uid)...... because it is not for just one UID. if there a way to 'skip' over the .child(uid) and .child(listingID) when pulling from firebase?