I am a 40 yr old army officer serving in the rank of a colonel. want an mba degree to join the united nations. what will be the best course

I have 23 yrs with the army. have been an instr for young and middle level officers. have been a commanding officer of an infantry battallion and been a military observer in sudan for one year. have 69%mks in class 12th and a bsc degree from JNU