Minecraft World not in the list after computer restart

I was playing Minecraft and then my computer started lagging so I turned it off and on back again, when the computer was on, I clicked on Minecraft and the world was not there. Luckily, it was in my files, but the problem is, it is not in the list on Minecraft. I think it has been corrupted or something, but I don't know.

Is there a way to fix this issue? Thank you!