Transfer Minecraft worlds from pc to mac?

I want to transfer my minecraft worlds onto my mac (I originally had a pc) but i don't know what folder(s) i should save my worlds to. I downloaded the game, i put my minecraft worlds into my flshdrive if this helps. I'm also logged into mine craft.

Also someone had told me that i need to install something called "Explorer". I'm wondering if that means internet explorer. If anyone knows, that would be helpful.

It not Internet explorer it's Iexplorer it can go into your phone apps, or backup stuff!
But I don't know how to backup it! I think you can save your flash drive to Mac or PC and then it might work! I don't know it doesn't hurt to try?