In a double-helical B-form DNA, the distance between two adjacent base pairs is 0.34 nm $=0.34\times 10^{-9}$ m.

Number of base pairs $=\frac{\text{total length}}{\text{rise per bp}}=\frac{1.1}{0.34\times 10^{-9}}\approx 3.3\times 10^9$ bp.