According to the Boyle's law, the volume is inversely proportional to the pressure at the constant temperature.

$\mathrm{PV} =\mathrm{nRT}$

At constant temperature, $\mathrm{P} \propto \frac{1}{\mathrm{V}}$

As we can see by the graph that the volume is increases at the constant temperature. The correct order of volume is ${\mathrm{V}}_1>{\mathrm{V}}_2>{\mathrm{V}}_3$. Then the pressure will decrease. So, the Order of pressure is ${\mathrm{P}}_1<{\mathrm{P}}_2<{\mathrm{P}}_3$.