The snapshots you need are the ones for the MOVIES and TVSHOWS datasets. Don't look at shares, that's not very helpful - they don't describe where the source folders are on the FreeNAS.
The images you've added all show the emby/root filesystem, which is not where movies etc are stored, just the metadata and emby itself.
Go to Storage, Pools and identify which dataset(s) the MOVIES and TVSHOWS shares are in. You may need to refer to Sharing, Windows Shares entries for MOVIES and TVSHOWS if you're not 100% sure.
Now go to Storage, Snapshots and look for snapshots of those datasets. Roll them back to the 15th.
If you don't have any snapshots of them, you're out of luck (unless you have backups).
But actually, I still think that you have all the original movies etc still, just that Emby has lost the references or some such thing. If you look in \\freenas\\javierdata\\MOVIES using Windows Explorer, are they really zero bytes?