Welcome to the QuickBooks Community! I'm happy to assist you to switch from QuickBooks Desktop to QuickBooks Online.
Before we begin, you'll want to update QuickBooks and run the Verify and Rebuild data utilities to make sure your company file is free of issues.
It's important to note that not all features and data from QuickBooks Desktop will be transferred to QuickBooks Online. I recommend reviewing the list of supported and unsupported features before proceeding with the conversion. Learn how features and data move from QuickBooks Desktop to QuickBooks Online.
To export your data, please follow the steps in this article based on the desktop product you use: Move your QuickBooks Desktop file to QuickBooks Online. It also provides some references and steps that you can follow after the conversion.
Let me know if you need help in the process. Take care and have a good one!