After searching over the internet I found a vMail OLM to PST converter, this Software is capable to convert multiple Mac OLM files to PST without any restriction; it allows you to convert multiple OLM files into a single PST file. Supports all versions of MS Outlook 97, 98, 2000, 2003, 2007, 2010, 2013, 2016 (Both 32 bit and 64 bit) and all updated Windows OS versions. 

Know more info- https://www.vsoftware.org/olm-to-pst-converter.html