Some popular Mastercam post processors include:
Open Mastercam, go to the File tab, and select Shared Mastercam [Version] . Navigate to CNC_MACHINES and then to the folder for your machine type (e.g., Mill, Lathe). Mastercam Post Processors Download
For Mastercam 2024 and newer: C:\Users\Public\Documents\Shared Mastercam 2024\CNC_MACHINES\ go to the File tab