How did Harry Potter know about the hufflepuff cup?

Answer 1

Hogwarts was the only place Tom Riddle (Voldemort) had ever felt truly at home, and shortly after arriving there, he became obsessed with his heritage. Dumbledore showed Harry a memory of Tom visiting Hepzibah Smith, who showed him two of the later horcruxes, one of Ravenclaw's (the diadem), and one of Hufflepuff's (the cup), which he later killed Miss Smith just for these two items. Harry and Dumbledore were able to deduce that Voldemort would look for other important objects relating to his heritage.

Answer 2

As they had broken into Gringotts they had to escape on a dragon. When they land they attempt to set up camp but not before Harry reads Voldemort's mind. Voldemort knows they are after the Horcruxes and decides to check on them. He thinks that the one at Hogwarts is the safest allowing Harry to know where it is, they then set off for Hogwarts to get the last Horcruxes.

Answer 3

Because Lord Voldemort is a little sad he got into sytheren and not hufflepuff because hufflepuff is the best one and he did not want others to think he was evil and he did not get in hufflepuff so it is his way of cursing hufflepuff and harry can hear them

Answer 4

From a vision in a pensieve Dumbledore had shown him.

Answer 5

Dumbledore showed him a memory where Voldemort learned about the locket and the cup. The woman who had these items turned up dead. Voldemort had them and made the horcruxes