If any kind of jpg to raf conversion is even possible, it would be graphics export related to Fuji graphics format. But everything points to the fact that RAF format is a RAW format used by Fujifilms, which means exporting random JPEG pictures to it does not make much sense as all the metadata that would be otherwise recorded by the camera will not be present.
In any case, if you need to work with RAF format, tools that work with digital photographs are your best choice in this matter.
Updated: October 10, 2023