Work out your max drift = 60 * Wind Speed / TAS.
Your drift will be equal to max drift if the wind is a >= 60deg cross wind. It will be three quarters if the cross wind is 45deg, half max drift if the cross wind is 30 deg, quarter if 15deg, you get the idea. Use your analogue watch face to get the fraction.
Assuming 100kts TAS. You max drift is 5 * 60 / 100 = 3deg. Your cross wind angle is 250-120 = 50 deg so you could round your drift to 3 (more than 3/4), wind from starboard so you should initially steer 122.
If the wind were 150/20 then your max drift would be 12deg. The cross wind would be 30deg and so your drift would be 6deg port so would need to steer 126.