If you have removed Outlook from Mac then there is likely to be a folder of old OLM archives which cannot be opened. As Outlook OLM is exclusive to Mac it will not be accessible on Windows. However, if you install Outlook again, you will have to create a profile to access your previous emails.

In order to access these archives you have to use workarounds which can cause issues. Installing Outlook can cause large resource usage, you could also risk altering the original archive. Converting to another client will alter the data. If it is a business archive this might not be desired. Using online converters requires transferring your emails to their server.

What you really want is an easy way to read the archive without converting.

Kernel OLM Viewer does exactly this. It is absolutely free and allows you to view OLM files on Windows (which is usually the issue). The tool can also open corrupted or damaged files. It allows you to view multiple archives. You will be able to view your emails, attachments, contacts, calendars and tasks all within the original folder structure.
https://www.nucleustechnologies.com/olm-viewer.html
How are you getting on with your old OLM files?