S.P.
S., there is very little pro bono assistance available, and what is available is "triaged" out to help the most needy. In your case, since you are already out of your abusive situation, it's unlikely that you will be able to get pro bono help.
However, having said that, you can still possibly do what you need to do for free, if you are willing to do the work yourself. Go down to the Clerk of the Court during business hours and ask the people at the desk for materials to file for a change of custody. They should give you everything you need, and at least some advice for filling it out (although not legal advice). You will usually need to demonstrate some significant change of circumstance to get custody reconsidered. There used to be a lot of helpful information online through maricopa county, too. Good luck to you.