According to Genesis, Noah took one pair of every unclean animal onto the Ark.
Genesis 6–9 describes the Flood story and distinguishes between clean and unclean animals. In Genesis 6:19–20, Noah is instructed to bring two of every kind, one male and one female, which establishes the familiar pair-based image of the Ark. A later passage, Genesis 7:2–3, gives a more detailed instruction: seven pairs of clean animals, one pair of unclean animals, and seven pairs of birds.
The two passages can appear different because they preserve different levels of detail within the narrative. The clean-animal distinction is associated with later sacrifice and ritual practice, while unclean animals are represented by a single breeding pair. The answer is therefore not two pairs: the standard Genesis 7 specification for unclean animals is one pair.