You should go to iCloud to see if your lost files are backed up previously or restore the files from the backup if you have one. If there is neither, then it's a pity that the files are all gone away and you have no chance to recover them back.
Take care~
If your external hard drive says it's full but isn't on your Mac, you can follow the tricks in this post to make it back to normal.
This post is an introduction to the iCloud Backup function on iPhone and iPad, including what the iCloud Backup is, how to back up iPhone/iPad with iCloud, how to restore from iCloud Backup, etc.
