N is force and kg is mass, so they aren't really the same The best you can do is use F=ma and thus N=9.8 kg-m/s^2
N = kg(m/s^2). If you are near the surface of the Earth... Take the mass, in kg, and multiply that by 9.8 m/s^2 (acceleration due to gravity near the surface of the Earth). As an example. An object...
Kilograms to Newtons, just multiply the Mass in kilograms by 9.81 and you will have your Newtons
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.