Convert .olm files to mbox and then import to apple mail.

I have a huge collection of emails that are very important to me saved in outlook 2011 and are no more available on the server, they got deleted some how. I need to transfer all these emails from outlook 2011 to apple mail. I used the import/export wizard of outlook 2011 and it created a folder that contains all my emails and sub-folders in .olm format. This folder cannot be imported into apple mail as there is no option to import from outlook 2011 or import .olm files. So I need to convert this folder into .mbox format so that it can be imported to apple mail. So any ideas or solutions on hoe to convert .olm files to .mbox???