A unit rate(called a unit price here) is a rate that compares to things. A common example that you probably know is miles per hour (emphasis on the "per").
We need to find the cost for each towel. The cost for 2 towels is $6.48. To find the amount of money per towel, divide 6.48 by 2.
6.48/2=$3.24 per towel
:)