I need help on describing how to prepare a buffer solution with pH=9? I'm terribly confused..?

Buffers are generally prepared by mixing a weak acid or base with its conjugate base or acid (usually in the form of a soluble salt), respectively. Acetic acid is an obviously wrong buffer because the pH for reasonable concentrations of acetic acid and acetate will be < 7. Ammonium has a pKa of about 9.25 (pKa = -log(Ka)), so it can be adjusted slightly by to get a pH=9 buffer by altering the ratio of acid to base. The base that you will want to use is the conjugate base of ammonium, which is the acid in this case. The conjugate base of ammonium is ammonia, NH3. So the NH3Cl / NH3 buffer is the best choice (and you would need about 1.8 times as much ammonium chloride as ammonia to acheive pH=9).