Are you Muslim? It's in the Quran.
It’s not mentioned in the Quran that all humans are descendants of Noah. However, the Quran mentions that Semites/Semitic peoples are descendants of Noah: Arabs 69:11 and Israelites/Hebrews 17:3:
[17:3] "O˺ descendants of those We carried with Noah ˹in the Ark˺! He was indeed a grateful servant."
The flood of Noah was limited to certain people only. It came to limited people, perhaps a village or a group of villages:
[7:59] We sent Noah to his people. He said: "O my people! worship God! ye have no other god but Him. I fear for you the punishment of a dreadful day!
[26:105] "The people of Noah rejected the messengers..."
The Genesis flood narrative and "that all humans are descendants of Noah" are two errors in the book of Genesis and the Genesis of Pentateuch is a product of the encounter with hellenism. The Pentateuch was written by a team of Jewish scholars around 270-323 BC (The Hellenistic period). The Torah scrolls that was written by Ezra the Scribe was destroyed or lost and a new version of the Torah was needed.