We define a user story as a thin, vertical slice of functionality that describes a small increment of value for the user (or customer).
On the other hand, a task is a step taken by the development team in order to meet the requirements of the user story. In general, a task should take between half a day and two days to complete.
As a result, the question should be what are the steps the team needs to follow in order for the story to be considered complete?
Whether you recognize it or not, your project has an architecture. It might be anything from a master piece drawn out in painstaking elaboration by the architecture team, to a high-level conceptual architecture diagram. Consider which components in your system need to be modified (or added) for the story.
Of course, just coding your story won't suffice to complete it. In Scrum, “done” means ready to ship, or as I like to define it: the story is as it will be received by the customer/user. Agile teams have a list of requirements that should be true for any story they complete. You should look at your Definition of Done (DoD) to see what tasks remain.