There are many manual tips available for OLM to PST Conversion such as:-|
Create an IMAP account
Configure with Outlook for MAC
Synchronize IMAP account with Outlook for MAC
Move data to IMAP account
But In manual tips, there are some limitation available which is harmful for your data. It has very long and complex steps which is highly time consuming. You should be technical person to perform the manual techniques otherwise huge risk of data corruption will be occured. So, to prevent these corruption you should use any third party software.
Here I'll suggest you this OLM to PST Converter Software which can easily convert all OLM files into PST format and also save converted OLM files in other format such as pdf, eml and msg file. It interface is user friendly and allow all users can easily use this software without any technical skill. It provde free demo version that help the users to know more about OLM to PST Conversion.