To convert QuickBooks Online data to Sage 50, you'll need to export your data from QuickBooks Online and then import it into Sage 50.
Here are the general steps you can follow:
Export your data from QuickBooks Online:
Log in to your QuickBooks Online account.
Click on the "Settings" gear icon in the upper right corner of the page.
Select "Export Data" from the drop-down menu.
Select the data range you want to export.
Choose "Sage 50" as the file format.
Click "Export" and save the file to your computer.

Import your data into Sage 50:
Open Sage 50 and click on "File" from the top menu bar.
Select "Import/Export" from the drop-down menu.
Choose "Import Records" and select "QuickBooks" from the list of options.
Browse to the location where you saved the QuickBooks Online data file.
Select the file and click "Next."
Follow the on-screen instructions to complete the import process.
Note that there may be some limitations and differences between Convert QuickBooks Online to Sage 50, so you should review your data carefully after the conversion to ensure that everything transferred correctly. Also, you may need to make adjustments in Sage 50 to match your business processes and preferences.