I'll assume that compared to the size of the ISS, the geomagnetic field is uniform over a small region. In that case, could that magnetic field be measured inside the ISS? To illustrate the question:
If we consider a cross-section of a module on the ISS (a cylinder), what does the magnetic field look like inside?
It seems the wall is made of a layer of ceramic-fiber or kevlar mesh material between the exterior thin aluminum sheet (2mm) and the aluminum pressure hull (3mm). [ref1, ref2], so the surface is a conductor.