Since the Business Analyst API for Flex is built on top of Adobe Flash 4 and ArcGIS API for Flex 2.x, first follow steps to migrate your Flex application from ArcGIS API for Flex 1.3 to 2.x. See the sections in the ArcGIS API for Flex site:
Once you have done this, you can make your Business Analyst Online API 1.0 code work with Business Analyst API for Flex 2.x. The easiest way is to open your code in Flash Builder 4.5 and step through all the errors, navigate to each line throwing the error. Double-click the error under the Problems View in Flash Builder or by manually going to the error in the source code. For example, if Flash Builder canít find a class, put the cursor at the end of the class, click Ctrl-Space and Flash Builder will import the class.
If Flash Builder can't fix the error, in cases where a class has been renamed, refer to the Whatís New for specifics on changes.