How do you convert 18 meters to centimetres?

Hint: Take the basic reference of conversion of meters to centimetres i.e. $1m=100cm$ . For 18 meters, multiply both the sides by 18 to get the required conversion. Then check the units of both the sides.

Complete step by step answer:
There are two types of systems of Units. They are MKS (meter- kilogram-second) and CGS (centimetre-gram-second).
Meters: Meter is the fundamental unit of length in MKS or SI (International system of units). It is defined as the length of the path travelled by light in vacuum during a time interval of $\dfrac{1}{299792458}$ of a second which can be denoted by ‘m’.
Centimetres: Centimetre is the base unit in the CGS system. It is used in measuring length for many everyday measurements. A centimetre is equal to $0.01$ meter which can be denoted by ‘cm’.
Coming to the conversion part
We know, $1cm=0.01m$
Multiplying both the sides by 100, we get
$\begin{align}
  & 1cm\times 100=0.01m\times 100 \\
 & \Rightarrow 100cm=1m \\
\end{align}$
We can write it as
$1m=100cm$
Since we required to convert 18 meters to centimetres
Hence multiplying both the sides by 18, we get
$\begin{align}
  & 1m\times 18=100cm\times 18 \\
 & \Rightarrow 18m=1800cm \\
\end{align}$
This is the required conversion.

Note:
Conversion should be done according to the proper unit conversion of meter to centimetre. In general the basic unit for reference is $1m=100cm$ . After conversion the units on both sides should remain the same. Meters and centimetres are the basic units of length that are used in our day to day life widely.