What are you talking about?
Matthew 24:35 Heaven and earth will pass away, but My words will by no means pass away. 36 “But of that day and hour no one knows, not even the angels of heaven, but My Father only. 37 But
as the days of Noah were, so also will the coming of the Son of Man be. 38 For as in the days before the flood, they were eating and drinking, marrying and giving in marriage, until the day that Noah entered the ark, 39 and did not know until the flood came and took them all away, so also will the coming of the Son of Man be.
Jesus indicated that the days leading up to "the coming of the Son of Man" would be like the days of Noah that led up to the coming of the flood. I assume you can understand that much? Yet, shortly before that, Jesus said that the coming of the Son of Man would occur "immediately AFTER the tribulation of those days".
Matthew 24:29
“Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light; the stars will fall from heaven, and the powers of the heavens will be shaken. 30 Then the sign of the Son of Man will appear in heaven, and then all the tribes of the earth will mourn, and
they will see the Son of Man coming on the clouds of heaven with power and great glory. 31 And He will send His angels with a great sound of a trumpet, and they will gather together His [a]elect from the four winds, from one end of heaven to the other.
So, how are you concluding that the coming of the Son of Man in Matthew 24:35-39 is pre-trib when Jesus explicitly taught in Matthew 24:29-31 that the coming of the Son of Man would be post-trib?