Quick STL Export From AutoCAD

I have an existing AutoCAD design for a product prototype that simply needs to be taken the last mile: generating a clean, watertight STL file suitable for 3-D printing. The geometry is moderate in complexity—medium... (Budget: ₹600 - ₹1500 INR, Jobs: 3D CAD, 3D Design, 3D Modelling, 3D Printing, AutoCAD, CAD/CAM, Fusion 360, Solidworks)