Wavelength is the linear distance between two adjacent points with the same vibration phase on the wave propagation path, usually in nm.

Wave number is the wave number with the length of 1cm.

When the wavelength unit is cm, the wave number = 1/ wavelength. If the wavelength is in other units, it can be converted.

In addition:

Nano (nm), 1nm= 1 times -9 power m of 10.