I’d dress professionally, but in way that makes you feel the most confident. Because that will always show through in an interview. I checked out what Macy’s asks for interview attire, and all it says is “Applicants should dress professionally yet comfortably” (clicky). Their dress code for the sales associates (available here) is essentially all black. So if you have all black, you may as well dress to impress in the dress code for the position. Otherwise, just be your sweet self.
If I were you, I’d do black chinos, a button-up; and maybe a black tie, vest, or blazer. Similar to what A.D. did here.
Oh, and don’t forget to do some ironing.