Is Target a proper noun

Yes, the Word 'target' is a common noun, a Word for any target of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Target Street, Charleston, SC and Target Street, Auckland, New Zealand
• Hotel Target Inn, Rome, Italy
• Target Auto Body, Cleveland, OH
• "Target", 1985 movie with Gene Hackman, Matt Dillon
• "Soft Target", a novel by Stephen Hunter