Your best solution for SWF (shockwave) to FLA (Flash project) conversion would be to use one of the dedicated SWF decompiling tools like the SWF Decompiler, which can be used to recover a .fla file from .swf source. It is not perfect, but reliable enough to perform somewhat accurate swf to fla conversion.
It might not always work on very old .swf files though, but should work on FLEX based SWFs. After you have the .fla file you can work with it in any Flash authoring software.