The volume of the Great Lakes, per Wolfram Alpha [1], makes a sphere ~22 miles in diameter. The Great Lakes is ~20% of the world's surface fresh water.
Your number of 35 million cubic kilometers includes the Antarctic ice sheet, but the definition of "fresh surface water" sounds to me like it intends to exclude the ice sheets from the list.
Your number of 35 million cubic kilometers includes the Antarctic ice sheet, but the definition of "fresh surface water" sounds to me like it intends to exclude the ice sheets from the list.
[1] https://www.wolframalpha.com/input?i=%28volume+of+great+lake...