According to Genesis, Noah brought one pair of each unclean animal onto the Ark.
Genesis 7:8–9 describes animals entering “two by two,” male and female. Earlier, Genesis 6:19–20 gives the general instruction to bring two of every kind of living creature. This is the source of the familiar pair-based image of the Ark.
The account also contains a separate instruction for clean animals and birds: Genesis 7:2–3 specifies seven pairs of clean animals and seven pairs of birds in many English translations. That distinction is why the answer for unclean animals is one pair, not seven pairs.
Readers sometimes treat every animal category as having the same number. Genesis does not do that. Its narrative gives a general pair instruction and then adds a larger number for clean creatures, which Noah later uses in the offering described after he leaves the Ark.