The Steam Cloud provides an easy and transparent remote file storage system for your game. Files specified in the Auto-Cloud configuration or written to disk (created, modified, deleted, etc.) using the Cloud API will automatically be replicated to the Steam servers after the game exits.If the user changes computers, the files are automatically downloaded to the new computer prior to the game launching. The game can then access the files by reading them through the Cloud API or reading them directly from disk as usual. Avoid machine specific configurations such as video settings.The Steam Client does the work of ensuring that the files are kept synchronized across all computers the user may be accessing.Users can globally disable Cloud synchronization in the Steam Settings under Cloud by unchecking "Enable Steam Cloud synchronization for applications which support it."
Create > My Data > Save Profile. You can use this new object to assign an extension. This extension will be added to the end of the file name if missing and is how the DataModel knows which files belong to it.