Hi @john john ,
Per my test, .mmap file is not supported in SharePoint Online modern pages. There is no OOTB web parts can display a .mmap file on the modern page. I have tested to use File viewer web part and Embed web part, the results confirmed what I say.
As a workaround, I suggest you:
- convert .mmap to .jpg/.png and use Image web part to embed a .jpg/png file to the page.
The sample page effect is shown in the below screenshot.
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