convert the OLM files to Apple Mail archive

Apple Mail does not import the OLM format files. Apple mail can only import in MBOX format. Thus all you need to to do at this moment is- convert the OLM files to Apple Mail archive.

There is no freeware solution to this. Only a paid tool can get your mails converted in the right manner. It is important that you take a free trial of the tool before purchasing it. Not every tool is worth the price. Make sure; the tool offers a refund as a guarantee for their success.

The tool I tried on offered me much more at the reasonable tag. Gladwev's OLM Converter Pro is a brilliant tool in all aspects.