prepare chemical solution

I’m studying and need help with a Chemistry question to help me learn.

my teacher ask me to prepare 2 mg /ml in 3 ml meaning 6 mg of insulin

first sample should have 6 mg of insulin + Hcl I dont know how much should I add + Tht the concentration for that is 20 mM I dont know how much should I add

second sample should have 6 mg of insulin + HCl i dont know how much + water I dont know how much should I add

it must have same contraction for all

I asked my teacher and she said do some calculation I dont know how plz explain to me

and how to prepare 0.1 M of HCL