I'm far from an expert, but would you not do this inside your controller that has a function (method) for fetching the data from the api & then a function (method) for storing the data?
Any transformation that needs done to the data then would take place inside your store function (method).
@CamKem Thanks for your advice, but I am importing data from various customers in a lot of different formats and I suspect a huge amount of data mapping would make a mess of my controller.
I think the closest would be a DTO with child elements in the response having DTO of their own. This way, your application can rely on the integrity of the DTO and if you need to do any manipulation of the data (suCH as converting tou your own data types or enums, then you can do it in the DTO