the answer to 3a is .25 grams and it is because 0.001 times 250 equal .25. and milli is the 0.001 the answer to 3b is 3500 milligrams and it is because 3.5 times 1000 equals 3500. the answer to 4 i dont know for sure what it is because i cant see the bottom of the carton picture. PLEASE MARK AS BRAINLIEST