psd to emb conversion is often searched for in the context of making embroidery designs based on Photoshop graphics (.psd files) and indeed, many users are wondering whether it is possible to use Photoshop files for making embroidery files.
Vector graphics files are the optimal source for making embroidery designs, but raster graphics work too, especially logos and similar designs.
Most modern embroidery tools offer tracing tools under various names that allow users to process bitmaps, turn them into vectors, and digitize the stitching pattern from them. When it comes to .emb files in particular, these files form from Embird, and thus this software is probably your best option for this kind of export.