Here's an easy, if not always precise way to remember: * Hyphens connect things, such as compound words: double-decker , cut-and-dried , 212-555-5555 . * EN dashes make a range between things: Boston–San Francisco flight, 10–20 years: both connect not only the endpoints, but define that all the space between is included. (Compare the last usage with the phone number example under Hyphens.) * EM dashes break things, s…
The em dash is now a GPT-ism and is not advisable unless you want people to think your writing is the output of a LLM.
If you practice your skills, you will reap the rewards.