Nervous and need some advice or encouragement

So I’m 20 years old and spent the majority of my life taking care of sick family members, I am now in a position to be able to work but find myself a little intimidated. A while ago I was in a traumatic accident that took me a little while to recover from physically and mentally. I’m nervous about having to explain myself. I’ve never had a real job only volunteer work. 5 months in a hospital gift shop and 6 months in a library, is this enough experience to be considered for a cashier position at a florist/gift shop? Also how should someone approach mmanagement for positions? What makes someone hirable?