As I know All 3 words mean possibly/perhaps. They differ in % of possibility (My Japanese friend said so). But I am confused when to use which one properly?
they all have different uses.
かもしれない is used at the end of a sentence to say "it might" or "maybe" (20-40%)
He might go to the baseball game.
たぶん is used as a prefix to say "probably," or "maybe" (75% or above)
Are you going to go the baseball game?
もしかしたら is closer to "if" than maybe, but also "perhaps" and the closest translation I could think of is "if by some chance." Don't think it is associated with a percentage, but is sometimes even used in combination with かもしれない.
Because by chance they might be selling baseball cards at the game, would you mind buying me a pack?
EDIT: From some suggested edits, I think it's worth it to note that even I slightly misunderstand もしかしたら。 It really is three parts, もし、か(Q) and したら、where もし itself means if, and もしか itself means perhaps or maybe, "in case." The したら at the end roughly makes it into like "if perhaps it is the case," in which case in my original example, saying たら twice was redundant to the meaning.