I went to shop to get my car aligned and they told me that my caster needs to be replace. The car pulls to the right really bad. They said I need to get that fixed. Is the caster a a single part of the suspension or do I have to replace control arms and camber ?????

 

Didn't they tell you what would need to be replaced?
What suspension are you using? Stock? Aftermarket?
What wheels and tires?

 

Caster is not a part. Caster is a measurement of the angle of a line that passes through the center of your ball joints and its deviation from straight vertical.
It's quite possible you have a bent control arm. Do you have your alignment specs?