AutoCAD supports the Xsteel NC1 format and thus can be used to export it to a standard DXF file. NC1 is fairly uncommon format so this seems like one of the few choices available.
Convert Xsteel CAD drawing to AutoCAD DXF Drawing Exchange Format.
We have found 3 software records in our database eligible for .nc1 to .dxf file format conversion.
Microsoft Windows software - convert nc1 to dxf on Windows
Leading 2D and 3D CAD development software from Autodesk
Convert from nc1 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned nc1 to dxf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A BIM software from Tekla
Apple macOS / Mac OS X software - convert nc1 to dxf on OS X
Mac version of popular Autodesk AutoCAD software