To generate a .pim file extension when posting the NC file in the Newcam Waterjet program, you generally need to ensure that your post-processor is configured to output the correct file type. Check your post-processor settings or configuration options within the software to specify the desired file extension for the output files. If you do not have access to configure this, or if it is not functioning as expected, you may need to consult the user manual or contact the software's support for detailed instructions on customizing output file types.