Thank you for being a loyal QuickBooks Desktop user for over 20 years. I'm glad to hear you're considering upgrading to QuickBooks Online (QBO), @sharonakd.

Regarding the error you encountered when trying to set up the 30-day trial - this indicates you'll need an active QBO subscription to add your existing company file. However, you can manually migrate your data from the desktop to the online version during the trial period. 

On the other hand, you can learn more about the steps you should take after the process to ensure your data is ready to go from this article: What to do after you move from QuickBooks Desktop for Windows or Mac to QuickBooks Online.

In addition, you may notice differences and wonder about how books appear. Take a look at this article for more info: Learn how features and data move from QuickBooks Desktop to QuickBooks Online.

I'm still here if you need more data migrations assistance with your company file to the online version. Anytime I can help.