Hello Chloe,
They're asking for the distance around the crater. That is another way of asking you to find the circumference.
Formula for circumference of a circle: C = pi * diameter
So you would do 3.14 * 5000 and find the circumference. The number you get when you plug this in your calculator will be in units of feet.
I'll let you with that (easy) step of plugging 3.14 * 5000 in your calculator. You got this.