Objects and Mobs disappear in my survival world

I have a survival world that I have been working on for months and yesterday I opened my world and I have a trading hall with all of my villagers lined up in a cage and so I decided to take a look. When checking them out I discovered they were just gone not there anymore. I also saw that my dogs, minecarts, and armor stands are gone. I had diamond armor and an Elytra on my armor stand and is one of the reason I'm ticked off. I really need my things back and if you have the opportunity to fix this bug, that would be great. Thank you!