250g equals how many cups?
This is like asking "How many apples equal a breeze?". Grams are a unit of weight, while cups are a unit of volume. The answer to this question depends entirely on the material being considered.
Grams is a unit of weight measurement. Cups measure volume. While you can weigh different things and have them all weigh 250g, these items will not equal the same amount of cups. For example, 250g of salt would take up less "space" than 250g of popped popcorn. So, since all foods weighing 250g may fill a different amount of cups, your question can only be answered if you are asking about a specific food.