MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
One quick way would be to upload the obj to makeprintable.com and then when you reach to step 4, it will ask you what format would you like to download your file, you can always select STL. One of our hidden benefits of using MakePrintable is we can convert CAD files from one format to another. ;-)
Try uploading a Gcode and download it using STL.