On minecraft. My world synced to a 4 month old version of its self, and i really need help

Hello. so i have this world i have been playing on for months, and i have sunk hours into it. A while back i went to my cousins house when my world was just beginning, and i synced the data from my xbox to theirs so i could show them my world. Now
everything was fine after that and when i got home my world was the same. fat forward 4 months and im at my cousins house again syncing my world to show them how much it has improved. But this time it doesnt sync and stays as the old version of my world. I
thought it was weird so i was like ‘whatever’ and i didnt play. then when i get home my xbox automatically syncs from my cousins xbox, and turns my world to the version it was 4 months ago. So now my world is the old version of itself on both xboxs and i have
no idea what to do. I really need help, i dont want to lose everything. please help me

:)