If there are data in that app they should appear in your phonebook.
Maybe check that the problem isn't just that your phonebook isn't displaying the data. There are options to only display certain groups of contacts, so if you inadvertently set it to only display an empty category (e.g. just phone contacts when all of yours are stored as Google contacts) then the phonebook will appear to be empty. I don't know the Samsung phonebook, but you can usually select which contacts to display when in the main phonebook viewing tab of the contacts app.