World Gone

Hello!
My computer shut down because of low battery while I was playing Minecraft. When I returned to it, the world I have been working very hard on and was very proud of had disappeared. I tried following multiple tutorials of how to get it back but nothing has worked so far (I tried creating a new world an replacing it's files with my old ones but whenever I click on the new world, Minecrat closes and when I open it, the new world is gone too). I am devastated and would appreciate any kind of help.
Kind regards, muckatv