John wants to retire by the time is he turns $62$ years old with a goal of $$3,000,000$ in his retirement account. He is currently $50$ years old and has $$850,000$ saved in his $401K.$ If he plans to save monthly for the next $12$ years and expects a $9\mathrm{.}75\%$ rate of return, how much will he have to save monthly to achieve his goal? $($Be sure to show your calculator inputs in your response.$)$