You may want to look at DXF2GCODE on Sourceforge
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There are several third party software that can help to do this job. It is a wise decision that, ask for a demo before buy the software. If the demo version satisfies, you can.
You can try Scan2Cad, that makes it easy to directly export a vector image to G-Code. Next it helps to open up DXF file in Scan2CAD and save it as G-Code. After that there are three options while it comes to the G-Code file extensions. Scan2Cad supports .cnc/ .nc etc.