I am studying rock caverns lined with concrete for compressed air storage. I would like to know if it's possible to convert the permeability coefficient from m/s to m^2 or Darcy. Thank you.
The word "convert" is reserved for units that measure the same quantity (like distance in inches or cm). In this case however you need to use the word "calculate" because the units are dissimilar. Yes, the Darcy's Law equation is what you are looking for.
In SI units, permeability "k" is measured in m2.
In SI units, porous medium gas flux "q" or "Q/A" is measured in (m3/s) / (m2) which reduces to m/s. Q is volumetric flowrate (m3/s) and A is area (m2). Algebraically rearrange q= Q/A as necessary such as Q= q × A.
So to calculate you also need the dynamic viscosity of air "µ" in kg/m-s. Note that this value is temperature and pressure dependent as you can see in this table.
You will also need the differential pressure in Pascals "Δp" in Pa or kg/ms2. The difference in pressure between the inside of our cave and atmospheric pressure.
And finally you will need the length "L" in meters. This is distance the gas must travel through the porous medium or in your case the thickness of your concrete layer.
When you solve the equation, you can confirm you used the correct units by canceling them out.