If you are looking for the Intrastat module, it is part of the Main GP install, I think fromGP2013 when more of the product extras were bundled in - but certainly from GP 2015. When running the GP installer the various features that can be installed are offered in the installer, find Enhanced Intrastat, click on the icon to change if it is installed or not by the installer. This can also be performed retrospectively to add the feature to an existing install.
You must switch the module on in company options and use the intrastat setup window to get it going. Look for the user guide on line or on the installation media for full details.