Cook 1 lb elbow macaroni in a pot of boiling water according to package directions. Rinse under cold water and drain.
In a small bowl together the dressing: Add 2 cups mayonnaise, ¼ cup milk, 1 Tbsp sugar, 2 tsp dried minced onion, ½ tsp salt and ¼ tsp ground black pepper. Mix together and set aside.
Add the 1 lb cold cooked pasta, ½ cup grated carrots, ½ cup chopped onion, 1 cup scallions (green onions), and 2 chopped celery ribs to a large bowl. Drizzle the white vinegar overtop and toss everything together.
Now pour the creamy dressing over top and mix the salad together.
Cover the salad and let chill in the fridge for minimum 4 hours. Give a quick stir just before serving.