importing pst file from outlook 2007 to outlook2011 mac – not all pst file readable

I just moved from window to mac and bough my self office365 personal.

I’ve imported my pst file (16GB) to outlook 2011 (mac) and the import process run perfectly.

However when I opened the import folder It only  shown very few emails and the worst is, there were mostly from the old email files.  

My first guess is because the difference file from outlook 2007 (pst) to outlook 2011 in mac (olm).

I tried to look up for pst converter to olm file software (in apple store or third party) but cannot find most suitable one.

anyone have similar problem and found the solution?, pls. share