Read/calculate permebility from BH curve
The relationship between B and H is \$ \mathbf{B} = \mu\mathbf{H}\$.  So if you have a B-H curve for a given material, you can find your permeability, \$ \mu \$, by finding B divided by H.  Keep in mind that permeability is a function of H, it is not constant for all values of H.

If you use standard SI units (Tesla for B and A/m for H), then your permeability units should be H/m.