The conversion from gallons to liters is equal to 1:3.785 respectively.
So therefore, if we have a specified number of gallons like we do in this question, we can multiply by 3.785 to find the number of liters:
[tex] 1.3x10^{15}gallons*3.785=4.92x10^{15} liters [/tex]
Therefore, Lake Michigan holds [tex]4.92x10^{15} liters [/tex] of water.