SolidWorks eDrawings files (such as .edrw) are foremost used for exporting or publishing purposes, which means they can be viewed but not further edited. Whenever it is possible to edit or export the drawings largely depends to the export settings, i.e. if the files were 'locked' during the export. Unlocked files can be perhaps opened in SolidWorks (or other 3D modeling tools with eDrawing plugin of sorts) and saved as standard files. As for locked files, this is likely not possible.
Your best option to achieve edrw to dwg conversion would be to actually obtain the original source and export that.Open EDRW file Open DWG file
A 2D and 3D CAD construction software