I was reading an article that explains the Infrared sensor until I came to the wavelength region's section, which has been mentioned as the following:
The infrared waves typically have wavelengths between 0.75 and 1000µm.
a- The wavelength region from 0.75 to 3µm is known as the near infrared region.
b- The region between 3 and 6µm is known as the mid-infrared region, and
c- infrared radiation which has a wavelength greater higher than 6µm is known as far infrared.
A side-note: I took into consideration that that image is wrong, and I found this one, but I don't think it is right either.
0.75µm and 1000µm = 750nm and 1000000nm = 0.75x10^-6m (= 7.5x10^-7m) and 1x10^-3m (= 0.001m)
3µm = 3000nm = 3x10^-6m
6µm = 6000nm = 6x10^-6m