How to export Products CSV file:
Login to the Etsy admin area, go to Your Shop -> Settings -> Options and click the Download Data tab.
In the "Currently for Sale Listings" section click the Download CSV button to save the file to your computer.
Upload the downloaded file to the proper field in Migration Wizard.
Please note that if the downloaded file size exceeds 128 MB, contact our Support team to avoid any possible migration issues.
According to the same principle, export Orders and Order Items data.