Help, medication mg-ml, my friends cat!!!!!!?

okay so my friend devynn had her cats balls clipiedand two weeks after he started bleedin very bad so we brought him o the vet, now hes home and we have meds for him and we have the dropper that the other people gav him from when he had his balls clipt but its in ml not mg and we need to know how to convert 50mg into how many ml's, how many ml is 50mg???