How can i migrate my my emails files from my PC to my new Macbook air

Here is an Apple knowledgebase article specific to your question. And here isa more general knowledgebase article about transfering data from one computer (including a PC) to a new Mac.

Not to push you away from asking questions here, but did you know that if you go to Apple's main support page (there's a button to it at the top of this window) there's a text box where you can enter a question to find knowledgebase articles? That's generally the first place I go when I have a problem.