I need help with this questions! No idea how to solve this!

You will retire 20 years from now, and you think you will need an income of $6,000 per month for 20 years after you retire.

You will begin saving for retirement by saving$500 per month for the next 10 years. How much will you have to save each month in the 10 years after that to have enough to meet your retirement goal?

The interest rate is 9% APR.

Round your answer to the nearest dollar.