Bar of pressure is equal to

A pressure is defined as the normal force applied through a  liquid per unit area

$P=\frac{F}{A}$

The unit of force in newton

unit of area is $m^2$

A Pressure has a unit of Newton per square meter  called  Pascal.

$$\begin{gathered} 1 Pascal = 1\frac{N}{m^2} \\ bar=b \\ kilopascal = Kpa \\ i.e.1 bar = 100Kpa \end{gathered}$$