Can I convert a desktop file to online if I don't have access to the program, but have the file saved on a thumb drive?

Welcome to the Community and thank you for choosing our service, @scwsltreasurerqb.

During the conversion process, you'll need to go to the Company menu on your QuickBooks Desktop program to convert the file. You can use a trial version then move your company file to another folder on your computer. You can check this article for your guide: Move your company files to another computer.

Once the Desktop file is ready, you can now import data from QuickBooks for Windows to QuickBooks Online. You can watch our video tutorial on how to get this done.

If you have additional questions, you can always hit the Reply button below. I'm here to help. Enjoy the rest of your day!

@scwsltreasurerqb 

It depends on your current version (year). Open it on trial license of Pro 2020 as mentioned by IntuitLily. You will get the error message if your version is too old. You have to call and ask Intuit Data Service to convert it or purchase a 3rd party conversion service.