the * is denoting the conversion from your first unit to your second, the / denotes the other way.

You have: 1 miles You want: feet * 5280 / 0.00018939394

In the above example, 1 mile is 5280 feet, and 1 foot is 0.00018939394 miles

If I do 2 miles to feet, the values are doubled (or halved for the reverse conversion)

You have: 2 miles You want: feet * 10560 / 9.469697e-05