In order to represent a number that is initially in nanometers but in meters, we will use scientific notation, which is a way of writing very large or small numbers in a better and understanding way.
1 nanometer = 1*10^-9 meters, this means that is 1 and 9 zeroes before this 1
450 nanometers = 450*10^-9 meters, but in scientific notation we only represent numbers within 1-10 scope, so 450 would not be a good idea, therefore the final representation will be
450 nanometers = 4.5*10^-7 meters