Is the muscovado sugar can be a substitute for the powdered sugar?

No, you can't. Muscovado is another name for minimally processed or "raw" sugar. I nickname that stuff "eye-boogers" because it looks like the stuff you wipe out of your eyes when you wake up lol. Because of muscovado's coarseness, massive size granules and lack of thickener (in comparison to powdered sugar), it is NOT a suitable substitute in recipes that call for powdered sugar. You can TRY to make powder of it with 2 parts sugar/1 part cornstarch IF and only if you have a food processor. But I can't recommend it as that's something even I have never tried before. I can't really help much further because you didn't describe what recipe you're trying to substitute powdered sugar for or why you need to substitute it.