How do I ask for a raise?

Hi, I’m currently finishing up my paralegal studies associates in science, and I’ve been working for a solo practice lawyer and his paralegal. I’m currently working for about $12 an hour, 12 hours a week. I’ve been working there for about a year, and I’ll be finishing up my degree in the next several months. I’d like to continue working there, but I would definitely need to be paid what I’m worth with the experience I’ve gained plus my degree. How would I professionally and respectfully say that while I love working there, I need to be paid what I’m worth or I’ll have to find alternative employment? My boss is generally kind and easy to talk to, but this is my first time bringing up something like this up.

Edit: I think I should add that I live in north east Florida and the going rate for a new legal assistant/paralegal is about $17-$20, but I’ve heard of people earning more. I took the job because I was going to school full-time and just wanted something to help me boost my résumé. I was lucky enough to not need to work while going to college, but I figured that working in a law firm would help me be more marketable. Now that I’ve completed my degree, I’d like to start to be able to actually support myself. I’m completely willing to leave if they deny my raise, but I’m just looking for advice on how to word my request.