Cuber!

Consider a 3³cube made out of 27 hollow subcubes. The subcubes are connected by doors on their faces(so every subcube has six doors, although of course some cubes have doors that open to the ‘‘outside’’). At least how many "moves"(travelling in a straight way is called a move) do you need to start at the center cube and visit every other cube exactly once?

You can take only $90^\circ$ moves horizontally, vertically and up-down.

N.b : This is a modified problem.