problem with world save folder

I recently got a new computer and I wanted to transfer my main survival world to it but when I went into the world saves folder of my old computer, it wasn't there.

(my old computer is a hp windows 7 my new computer is a Lenovo Windows 10 and i play java edition on both)

the world saves folder on my old computer had every single world I ever created on it EXCEPT my main survival world (its called WerewolfRatFMS Survival). I did transfer all the other worlds onto my new computer just to check if I had accidentally renamed it or anything but none of the worlds were my main survival world.

in short, one of my worlds is not in my world saves folder. I can still play it, its just not in my world saves folder so I have no way of transferring it onto my new computer.

I really need this bug fixing