Hi Rob,
Thank you for your quick response. At first, I sent them the step file but they said they could not open it. Then, I checked the CAD supported list and sent them the DWG and DXF files, but they still could not open it. I am thinking about trying the JT file for one more time but they just ask me to send them the .nwd file so I am not sure if there is an workaround to convert NX to .nwd