You can use many assets that are available for free and paid in asset store.
Save Game Free - XML and JSON saving and loading.
Syntax:
Saver.Save (T data, string fileName);
Example:
Saver.Save (myData, "myData"); // The .json extension will be added automatically
Save Game Pro - Binary saving and loading. fast and secure. Easy to use.
Syntax:
SaveGame.Save (T data, string identifier);
Example:
SaveGame.Save (score, "score");