Quick Answer
Heavy Cream does not use the same grams-to-cups value as every other ingredient. Using a practical US cup reference, 238 grams of heavy cream is about 1 cup.
That means 100 grams of heavy cream is about 0.42 cups, while 200 grams is about 0.84 cups.
Heavy cream is slightly denser than water due to its fat content, with one US cup weighing around 238 grams.