1. We need 2 cups of flour.
2. We need 40 grams of butter.
3. We need 100 grams of sugar.
(Are they all grammatical?)
4. We meet 9:00 am on April 3.
5. We meet at 9:00 a.m., April 3.
6. We meet on April 3 at 9:00 a.m.
7. We meet April 3, 9:00 a.m.
(Which one is grammatical? Thank you for your help.)
1, 2, 3, 5, 6 -- all are correct.
4 and 7 are expressions I've not heard much.