The synchro-server module is part of the Synchro Server project, hosted at https://github.com/SynchroLabs/SynchroServer
This module is typically not installed directly via npm, but by using the Synchro Command Line Interface (CLI), which uses npm to install its modules.
For more information on installing Synchro Server, see the Synchro CLI package: https://www.npmjs.com/package/synchro