Hello,
You've almost got it. Add a period after CDC. The title, Attention-deficit/hyperactivity disorder (ADHD) should be sentence case as I've typed it here. It should also be italicized. You can take the National Survey of Children's Health out completely. Remove the colon after Retrieved from. Remove the period after the CDC url and remove the date as well. So:
Centers for Disease Control and Prevention. (2018). Attention-deficit/hyperactivity disorder (ADHD). Retrieved from https:www.cdc.gov/ncbdd/adhd/data.html
Also, don't forget your hanging indent.
