Let
X/Y--------> the ratio
we know that
X/Y units --------> are inches/yards
9 yards*(X/Y ) inches/yards-------> 9*X/Y yards*inches/yards----> 9*X/Y inches
the ratio in this problem is (X/Y inches /yards)-------> 36/1 inches/yards
the unit in the numerator of the ratio is inches
the answer is
inches