As there is unavailability of any inbuilt functionality to convert Mac Outlook OLM files to EML format. But you still can convert OLM to EML with GSTECH Mac OLM File Converter. It precisely converts and export Mac Outlook OLM file to EML with associated attachments. Apart from it also offers to save contacts and calendars to vcf & ics file format respectively.
Know more info-https://www.gstechsoftware.com/olm-to-eml-converter.html