A human body has iron in it , if a magnet is placed (strong or weak) will the iron attract it , if not then why not ?

Simply, because the metals present in the body are small in relation to any magnetic pull. I add that most metals in the body are suspended in fluids or tissue (such as), thus they are not condensed into a "brick" or "node" that can react to the magnetic influences.

Iron in crystaline form responds to magnetic fields, Iron in an organic compound does not.

Hemoglobin in our blood contains iron. In this molecule, iron is a positive ion. In this form iron is not magnetic. The most common form of an iron supplement tablet contains iron sulfate. In this compound, iron is +2 ion.

The state of the iron is not magnetic.