A map of the the Sigma Draconis system
Sigma Draconis II was the second planet in the Sigma Draconis planetary system. This was one of six planets in this system that was not classified as M class; the others were Sigma Draconis I, Sigma Draconis V, Sigma Draconis VII, Sigma Draconis VIII, and Sigma Draconis IX. (TOS: "Spock's Brain")
Presumably, Sigma Draconis II was located in the Alpha Quadrant.
According to the Star Trek: Star Charts (pgs. 19, 44), Sigma Draconis II was located in Sector 004 (Sigma Draconis sector).