The client resource file, SPCClientResources.resx, is located in the Localization subfolder of the Smart Construction installation location (browse to [Drive]:\Program Files (x86)\SmartConstruction\2019\Customization\Localization).
Make a copy of the original SPCClientResources.resx file, and save it as a backup file in a different location than the Localization subfolder, in case you need to recover it later.