Status needs to be swapped from IRR to Active Duty Army?

SGT (Join to see), you'll have to have your status changed in DEERS before that happens.

Are you assigned to a unit yet? If so, your personnel folks (PAC, S1, etc) should be able to take the lead on getting this done.

If you are going through a MEPS or recruiter, talk with them as they should have taken the lead on getting this resolved.

If nothing else, you can take a copy of your orders to your nearest military installation's RAPID site (https://idco.dmdc.osd.mil/idco/locator) and work it that way. If you can't make an appointment in the near future, you can (may vary by location) show up as a walk-in and get it done.

Hey, I was in your shoes 5 years ago brother. When you enlisted into the army you signed a Conditional Release to the Marine Corps (for your IRR Status). This paperwork should be on IPERMS which any S1 (Admin) can lookup for you. Get with your S1/Deers Office to ensure that all your documents are good to go. Also, it should've been automatic to be honest. How long have you been in the Active Army? Feel free to shoot me a PM if there's anything you need answered regarding prior service. (I went Marine Sergeant to Army Sergeant as well)

You shouldn't have to do any of this because whatever unit you are going to report to already should know you're coming and be expecting you. They should have taken care of all of this. Marine to army, I know you're not hitting up boot camp or anything, so you should have everything handed to you in a welcome aboard packet or something.