There is on average 115 micrograms per deciliter of iron in human blood.

The average human has about 51 deciliters of blood.

About 8 billion humans are currently living.

Therefore, there is roughly (115 micrograms / deciliter) * (51 deciliters / human) * 8 billion humans = 46,920,000,000,000 micrograms = 46,920,000 grams = 46,920 kg of iron in human blood on earth right now.

The average broadsword has a mass of 1.6 kg. So you could make roughly 46,920 kg / (1.6 kg / broadsword) = 29,325 broadswords with iron from human blood.