Q. Where does Minecraft Windows 10 edition save the game worlds?
A. Unlike the regular Minecraft which saves the worlds to location
%USERPROFILE%\AppData\Roaming\.minecraft\saves\, the Windows 10 edition saves the worlds to
LocalState\games\com.mojang\minecraftWorlds. The worlds save in different formats so you cannot just copy worlds from the java based version to the Windows 10 version.