How to delete a save/Reload an older save. PLEASE HELP!

my brother recently killed all entities on my group's aternos server, The game saved just before he did anything(as in when in chat it says [Server]: Saved the game), is there any way to revert to that version? I really need help, We didn't have backups set up and we haven't started the server again, so logs are still there, we set up backups after we shut the server down, is has 83 MB of data on it but I can't see what's in it because it's on a diff person's google, in the menu it also doesn't show any back ups of the server. Please help!