XGL 3D CAD models (.xgl) can be converted to all kinds of other 3D modeling formats, including STEP format (.stp, .step). You will have to either use some of the 3D modeling tool with XGL and IGES support, or some dedicated 3D model converter.
Convert XGL 3D CAD model to ISO-10303 STEP product data.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert xgl to step on Windows
A CAD viewer program with conversion capabilities
Convert from xgl file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.