I lived in North Carolina for a few yrs. I moved back to Arizona and my sons mom requested child support from me. I have 2 child support cases. One in North Carolina and one in Arizona. How can I modify them both and combine them into one case here in az?

The state that started it has jurisdiction so long as 1 party still lives there otherwise it will follow the child. That's federal law. So unless they moved from the original points you can't just move it close to you. It will be closest to the child so long as the minimum requirements for residency are met.