Am I eligible?

Okay I am 28yrs old, female, married. Okay so my dad who passed away in 2012 due to kidney failure i believe was in the military for the Vietnam war. He was technically my grandfather but legally adopted me so I am his legal child. I’m just curious am I eligible for a military ID? I have all his information and can get many more info I may need from my mother but I don’t want to waste time or look stupid