oops, i got the wrong end of the stick with that q, i take it u meant - before Moses (pbuh) made the request.
Allah only mentions what is relevant to that topic and leaves out the rest, and if necessary, mentions it elsewhere in a different context, again leaving out details which in His wisdom, are not relevant to that section.
A part of the conversation you seek is mentioned in another chapter in another context with a different lesson relevant to the topic of which Allah knows best the significance,
here:
83. (When Moses was up on the Mount, Allah said: "What made thee hasten in advance of thy people, O Moses?"
84. He replied: "Behold, they are close on my footsteps: I hastened to thee, O my Lord, to please thee."
85. ((Allah)) said: "We have tested thy people in thy absence: the Samiri has led them astray."
86. So Moses returned to his people in a state of indignation and sorrow. he said: "O my people! did not your Lord make a handsome promise to you? Did then the promise seem to you long (in coming)? Or did ye desire that Wrath should descend from your Lord on you, and so ye broke your promise to me?"
87. They said: "We broke not the promise to thee, as far as lay in our power: but we were made to carry the weight of the ornaments of the (whole) people, and we threw them (into the fire), and that was what the Samiri suggested.
88. "Then he brought out (of the fire) before the (people) the image of a calf: It seemed to low: so they said: This is your god, and the god of Moses, but (Moses) has forgotten!"
89. Could they not see that it could not return them a word (for answer), and that it had no power either to harm them or to do them good?
90. Aaron had already, before this said to them: "O my people! ye are being tested in this: for verily your Lord is ((Allah)) Most Gracious; so follow me and obey my command."
Quran 20:83-90 (Ta-Ha)
it seems to fit in with the verses you mentioned sis because he (pbuh) had left Harun (pbuh) in charge and the calf is again mentioned:
142. We appointed for Moses thirty nights, and completed (the period) with ten (more): thus was completed the term (of communion) with his Lord, forty nights. And Moses had charged his brother Aaron (before he went up): "Act for me amongst my people: Do right, and follow not the way of those who do mischief."
143. When Moses came to the place appointed by Us, and his Lord addressed him,
he said: "O my Lord! show (Thyself) to me, that I may look upon thee." Allah said: "By no means canst thou see Me (direct); But look upon the mount; if it abide in its place, then shalt thou see Me." When his Lord manifested His glory on the Mount, He made it as dust. And Moses fell down in a swoon. When he recovered his senses he said: "Glory be to Thee! to Thee I turn in repentance, and I am the first to believe."
144. ((Allah)) said: "O Moses! I have chosen thee above (other) men, by the mission I (have given thee) and the words I (have spoken to thee): take then the (revelation) which I give thee, and be of those who give thanks."
145. And We ordained laws for him in the tablets in all matters, both commanding and explaining all things, (and said): "Take and hold these with firmness, and enjoin thy people to hold fast by the best in the precepts: soon shall I show you the homes of the wicked,- (How they lie desolate)."
....
....150. And when Musa (Moses) returned to his people, angry and grieved, he said: "What an evil thing is that which you have done (i.e. worshipping the calf) during my absence. Did you hasten and go ahead as regards the matter of your Lord (you left His worship)?" And he threw down the Tablets and seized his brother by (the hair of) his head and dragged him towards him. Harun (Aaron) said: "O son of my mother! Indeed the people judged me weak and were about to kill me, so make not the enemies rejoice over me, nor put me amongst the people who are Zalimun (wrong-doers)."
151. Musa (Moses) said: "O my Lord! Forgive me and my brother, and make us enter into Your Mercy, for you are the Most Merciful of those who show mercy."
152. Certainly, those who took the calf (for worship), wrath from their Lord and humiliation will come upon them in the life of this world. Thus do We recompense those who invent lies.
Quran Ch 7, The Heights