To migrate the database from OLM Mac to Office 365 cloud account, one can go to download MailsDaddy OLM to Office 365 migration tool on a Windows machine. It is one of the safe and secure applications available in the market which can directly export OLM data to Office 365 account including all emails, contacts, calendar, etc.
This program does not require any additional program or knowledge to import all OLM files to Exchange Online. The OLM converter is a Windows-supported program that you can use on any Windows version including 10. Use the free demo version feature to freely access the entire program at no cost.
For more info: MailsDaddy OLM Converter