I want to write a story about a girl who grows up with a family involved in illegal drug trade, but no idea where to start?

You are too naive to create such a story. It is better to stay unable to write such a story.   Most women commit suicide.  Most of the guys are murdered unless they go to prison.

Write what you feel is right. The only people who will read your story and pick it apart for details that you didn't get exactly right are people who are involved in the illegal drug trade, and you don't care what they think because they're bad people. Watch some movies with characters in the drug trade (any action movie from the 80s and 90s) and start writing. Credit me if you make the bestseller list.