Question

How did Iron come to earth (millions of years ago)?

Answer 1

Iron is made inside stars.
Explanation :
Iron is made inside stars, specifically red super-giants. The elements form together inside a star during fusion. When the supernova occurs, the iron fragments are blasted into the space.

This is how Iron came to Earth millions of years ago. You can see the image below of a 20 Solar Mass $\left(M^{\circ }\right)$ star.