I lost my Survival world!

I had a great survival world in Minecraft Beta from January 2021 to April.

After this, I got out of the Beta version to play with my friends on Switch. I backupped the world but couldn´t join it because I wasn´t in Beta anymore.
After 1.17 released, I noticed, that I could join the world again. Today I wanted to play in the world and enjoy.

But I spawned in a big cave on Y=75. After this, I changed into Creative Mode and teleported my character 200 Blocks up. 

I finally saw my old Bridge, Village and my Farms again and was very happy.

But I noticed, that I was on Y=161 and clouds were floating on the ground.

All of my chests were competely empty and all entities (including Villagers, Armor Stands etc.) were missing.

 

 

I put a lot of effort and time in this world and would be very happy for Feedback.