In Genesis, Noah brought one pair of every kind of unclean animal into the Ark.
Genesis 6:19–20 instructs Noah to bring two of every kind of living creature, male and female. Genesis 7:8–9 repeats the distinction between clean animals and unclean animals entering in pairs. The unclean animals therefore appear as one male-and-female pair.
The passage becomes more complicated in Genesis 7:2–3, which tells Noah to take seven pairs of clean animals and one pair of unclean animals. Readers sometimes flatten these passages into a single number, but the text distinguishes clean from unclean animals and gives different quantities.
The phrase “every kind” belongs to the biblical classification in the story, not to modern biological species. Genesis does not present a modern taxonomy, and translations vary in how they render the Hebrew categories.