If I remember wel, 1 kg' (1 kilogramme force) = 9.80665 Newton or 0.980665 decaNewton.
So 1 daN = 1 / 0.980665 kg' or 1.01972 Kg'
45.3kg.
Multiply by 1000000. So 8 * 1000000 = 8000000 miligrams.
Easy. Just divide pounds by 2.2 to get kilograms. (If you need to be more precise in your calculation use 2.20462262 pounds instead of 2.2 pounds.
50 t(US) = 45359.237 kg
Simple - divide by 1000. That is, put the decimal point after the 4. There are 1000g in 1kg, so to convert grams to kilograms you always just divide by 1000.