jpg to bmc conversion is most likely used for the purpose of using pictures saved in JPEG format as basis for making new embroidery designs in BMC format, which seems to be used in some very old stitching machines.
Nonetheless, many embroidery tools still support saving to .bmc files for legacy reasons, so it shouldn't be hard to find one that can help you with this, just make sure it features some kind fo digitizing or tracing function (raster to vector).
Updated: October 24, 2023