Given the distance between two consecutive base pairs is $0.34 \mathrm{nm}=0.34\times {10}^{-9} \mathrm{m}$.

A total number of bases $=6.6\times {10}^9 \mathrm{bp}$.

Length of DNA $=$ Total no. of $\mathrm{bp}\times$Distance between two consecutive$\mathrm{bp}$

$= 6.6\times {10}^9\times 0.34\times {10}^{-9}$

$=2.24 \mathrm{m}$