Created worlds

When I open my Minecraft I go to play on my world when I click on my world it starts syncing user data for about 5-10 minutes then it says the migration or the sycing  process was corrupted  or couldn't migrate and I have never transferred my world it's just horrible I have done just about everything to try to fix this and because of this I am not able to play any of my worlds I have world that is about 3 or 4 years old And now all of a sudden and it won't work please fix this issue so I can play my beloved world again, this all started October 5th this year, and I have done everything to fix it and nothing works please fix this