Mobs, Villagers, Dogs disappearing in Minecraft... please help

So about a week ago i wanted to try out the Latest Snapshot of 1.17 Caves and Cliffs. Being the person i am i loaded my 1.16.5 world into the latest snapshot. when i tried going back to the latest release my mobs weren't there, no villagers, none of my dogs, Nothing... I read an article than snapshots are really buggy and next i should just create a new world if i want to check the next snapshot...

Now if i go into the world which is now a snapshot world all the mobs are there, but now i can't even access it because of "can't load old worlds thing"... How do i get my mobs back into the 1.16.5? please help

Me in Snapshot

• Thank You