Unknown Data Version: 0

Hello, I used to host a server on a 3rd party website, and everybody stopped using it, so my goal was to turn it into a solo world. I did this before and had no issue, but this time the world was up to date but my player data was not. I deleted the old level.dat and level.dat_old files and pasted my UUID files from the playerdata folder, but when i tried joining the world from the singleplayer menu this happened, and when I tried finding out more this happened. I expected it to update my data but instead the world just didn’t work.