I appreciate you reaching out to us about your Sage 50 conversion issue.
The QuickBooks Conversion Tool is a free program to help you convert your Peachtree data to QuickBooks. However, it only supports versions 2013 to present. To resolve the error you're getting and ask for other options I recommend reaching out to their contact help for guidance with Peachtree 2011 conversion.
They have the tools necessary to run your company file and process your request, @SPAR927.
Keep me posted on how it went or if you have other QuickBooks concerns. I'm always here to help you out. Have a good one.