The conversion in itself doesn't cost any action points, but you first have to spend actions to move each seperate cube to the order card.
After moving the two cubes to the order card they are (magically
) converted into a cube of another colour. This costs nothing.
Wrong, it costs 2 points to convert.
What? From the rules:
Important: Instead of the Coal cube of the
requested color you may place any 2 Coal
cubes (of the same or different colors) onto
the Order spot. However, moving these 2 Coal
cubes from your Pit cage to the Order spot still
requires a total of 2 work steps.