If you are a Compass user you can convert an existing Compass project to a Serve project with the "convert" sub-command:
serve convert mockups
This will rename and move a number of files for you and will turn your Compass project into a Serve project.
The convert command respects the same flags as the create command.
Note: After upgrading a Compass project, you will no longer need to use the compass watch command to generate your stylesheets. Your stylesheets will be compiled on the fly with Serve.