Genitive case of an interrogative pronoun pos (what) otherwise obsolete (perhaps the same as pou used with the rising slide of inquiry); as adverb of place; at (by implication, to) what locality -- where, whither.
KJV: Now the first day of the feast of unleavened bread the disciples came to Jesus, saying unto him, Where wilt thou that we prepare for thee to eat the passover?
NASB: Now on the first day of Unleavened Bread the disciples came to Jesus and asked, "Where do You want us to prepare for You to eat the Passover?"
KJV: And the first day of unleavened bread, when they killed the passover, his disciples said unto him, Where wilt thou that we go and prepare that thou mayest eat the passover?
NASB: On the first day of Unleavened Bread, when the Passover lamb was being sacrificed, His disciples said to Him, "Where do You want us to go and prepare for You to eat the Passover?"
KJV: And wheresoever he shall go in, say ye to the goodman of the house, The Master saith, Where is the guestchamber, where I shall eat the passover with my disciples?
NASB: and wherever he enters, say to the owner of the house, 'The Teacher says, "Where is My guest room in which I may eat the Passover with My disciples?"'