How many nanometers are in $1$m?

Hint: Convert the given value in the required specific units by using the conversion relation. Use the formula - $1{\text{ meter}} = {10^9}$ nanometers. Place the relation using the basic mathematical relations

Complete step by step answer:
We know that the basic relation between metres and nanometers.
$1{\text{ meter}} = {10^9}$nanometers
Therefore, the above equation can be re-written as -
${10^9}$nanometers $ = 1{\text{ meter}}$

Note: The units are the standards for the measurement of the physical quantities which needs to be clear to be useful. Units are the internationally accepted standards for measurements of the physical quantities.
Different types of system of units are –
SI (International system of units)
The SI units are the standards of measurement defined by the international system of units.
MKS (Meter-kilogram-second) system
MKS system is the system of units, where length is measured in meters, mass in kilogram and time in seconds.
CGS (centimetre-gram-second) system
CGS system is the system of units, where length is measured in centimeters, mass in grams and time in seconds.
 It is very important to know the difference between the system of units and the conversional ratios between them. Since if we say mass of one it does not make any sense, also mass of one gram and one kilogram differs a lot as $1kg = 1000g$ .
Always check the units of the given term, all the given terms should be in the same system and then start solving. Also, remember the conversional relations of the different physical quantities and apply accordingly.