How much does one cup of fresh spinach weigh?
How much spinach is in a cup varies widely based on who is doing the measuring, how well the spinach is trimmed, whether it is chopped, the size of the leaves, whether it is cooked, and if it is cooked, how well it is drained.

That said, the FDA calls 1 cup of raw spinach 30 grams.

If you're looking for the number of leaves in a cup, that can't be answered because some leaves are much bigger than others. To measure a cup, you need a cup, a scale (30 grams would work for raw spinach) or to be willing to guess.

EDIT Now that you've added the size of the leaves, the question is answerable, but I would need leaves that size and a cup in order to answer.