Crashed and lost an ENTIRE world I had been working on for months... Where are the game files stored on WIN 10 systems?

Minecraft crashed & I lost an entire world I had been working on for over a month... Where are the world files stored on the WIN 10 system ??? Also F3 never has worked in WIN 10 (F5 works fine) and that means the ability to auto insert coordinates into the commands doesn't work either... How can I find my lost world??? Thanks in advance.... TEACH PEACE!!!