I can help you restore your .dmg file, Chhassociation.
We offer 30-day trial links for QuickBooks Desktop. To convert the .dmg file to QBO, you'll have to do the round-tripping process first. This means that you will restore the file using a recent QuickBooks Desktop version, and then import it into QBO.
You can get the trial links through this article: QuickBooks Desktop trial links.
When your file is all set, you can follow these articles to help you convert it to QBO:
There you have it. Feel free to leave a message if you have any follow-up questions. I'll be right here to help.
As @SophiaAnnL mentioned, essentially what you have to do is convert your Mac into a QuickBooks Desktop QBW file with a trial version of QuickBooks Desktop. Once you have the file converted, you can then do the direct Desktop to Online Conversion.
We created a guide for how to convert from QuickBooks Desktop to Online - the first few sections proide guidance on the pros and cons of converting and whether it is right for you.