steez: You are neglecting to mention and key piece of informaiton. We need the concentration per unit volumn of the tamoxifen citrate. For example, it might be dosed at 20mg/mL which means that 1mL (1cc) contains 20mg of tamoxifen citrate.
As for the syringe, I do not know its size. Probably 1mL, but that's just a guess.