Ohm/sq is "Ohms per square". So a resistor that is say 50 Ohm/sq would be 50 Ohms if its width is the same as its length (W = L). It does not matter what W or L are but only the ratio of the two dimensions. Similarly if L = 2 * W it would be a 100 Ohm resistor or if L = W/2 the it would be a 25 Ohm resistor.
So the is no direct relationship between Ohm/sq and Siemens/m. The latter only has meaning if something is known about the cross-section of the material.