One mole of silver weighs more than one mole of iron. The mass of one mole of silver is 107.870 grams and the mass of one mole of iron is 55.845 grams. The mass in grams of one mole of a substance is called the molar mass and is found on most periodic tables.
One mole is 6.02 x10^23 particles, with the particles being atoms in the case of silver and iron.
Weight and mass aren't exactly the same, but something with more mass will weigh more (assuming we're not leaving the planet!). Mass is the amount of matter something contains, and weight is the force it exerts due to its mass and the force of gravity. When we "weigh" something we're indirectly finding its mass. Weight = mass x acceleratiom due to gravity. Everything on the surface of the earth is acted on by about the same force of gravity so it works to say that the sample in this case with more mass also has more weight.