In what type of Hebrew Rambam wrote the *Mishneh Torah*? 

I just started to learn Biblical Hebrew and when I have learned basics I will start to read Pentateuch in Hebrew with some helps. The next step will be Rambam. Now, should I also learn Mishnaic Hebrew or Modern Hebrew in order to understand *Mishneh Torah*?

Background: I'm not a Jew but I'm interested in Judaism. I'm pondering on conversion in the future.