I also have powdered milk in the pantry. Here's the table for turning that into different formulations of milk. To make one cup of milk or cream, just combine the following. (Put the cream in a measuring glass and fill to the one cup line with skim milk.)
1.5 teaspoons heavy cream = 1% milk
1 Tablespoon heavy cream = 2% milk
2 Tablespoons heavy cream = whole milk
5 1/3 Tablespoons heavy cream = half & half (1/3 cup cream and 2/3 cup milk)
8 Tablespoons heavy cream = light cream (1/2 cup of each)
Note: to turn 1% milk to half and half, use 1/4 cup cream and 3/4 cup milk.