Convert STL image of poackaging design to DXF and DWG files.

I have a product that I plan to sell. I need to have custom soft charcoal foam cut so that it holds and protects my product. I designed what I want in Sketchup and produced an STL file. None of the places that do the custom foam cutting work accept STL files to work from. I need to provide them with a DWG file which includes relevant dimensions, and a DXF file. I don't know how to convert this. I assume someone can load it into a CAD program and convert it to one or both of the outputs I need to get the product made.