SFW format comes from Sound Forge, where it acts as a project for editing audio content, and as is the case for any project files, these are tied to the original software only.
Projects typically do not contain original source data, just references to them, so sfw to at3 conversion is only viable as an export with Sound Forge and only if you possess the source files as well. Often done simply via Export as.. or similar function.
Updated: February 14, 2024