I am about to set up a new retirement savings account that earns interest at a 3.5% annual interest rate (APR). I want to make monthly contributions to that account from now until I retire. The goal is to save enough money so that I will be able to withdraw the money that I will need each month without depleting my principal ( in reality, I will probably deplete the principal gradually).

How much will I need to contribute to the account each month?

Please help me help me put this on paper. I don't know where to begin.