Essential University Physics: Volume 1 (3rd Edition)

We can find the number of hydrogen atoms as $N=\frac{1cm}{0.1nm}$ $N=\frac{1\times 10^{-2}m}{0.1\times 10^{-9}m}$ $N=\frac{1\times 10^{-2}m}{1\times 10^{-10}m}$ $N=1\times 10^8atoms$