Conversion of a permeability value from barrer to SI unit

I have done a permeability experiment on LDPE in the presence of air. At $\pu{30^\circ C}$, the permeability was found to be 1.846 barrer.


Now I am trying to apply this permeability value to a calculation whereby I am trying to find what the change in pressure of a dunnage bag is (it is a bag that has the shape of a pillow) after 5 minutes. I have the following info:


$$
\begin{align}
\text{Volume of bag}&= \pu{0.2064 m^3}\\
\text{Approximate area} &= \pu{1.35 m^2} \text{ (this is just a quick approximation)}\\
\text{Thickness of LDPE} &=\pu{ 0.042 \*10^-3 m}\\
\text{Time }&= 5 \times \pu{60s} = \pu{300s}\\
\end{align}$$


Is it correct if I convert barrer to SI units in the following manner?


$$\pu{1 barrer} = 7.5005\times10^{-18}\ \mathrm{m^2\ s^{-1}\ Pa^{-1}}$$


By using the following formula, I was hoping to calculate the change in pressure. However, my values don't make any sense at all!


$\displaystyle\text{Permeability} = \frac{\text{Volume}\times\text{thickness}}{\text{Area}\times\text{time}\times\text{Change in Pressure}}$


