Just got out of the IMA Reserves and looking to Traditional Reserves. Do I have to go back to MEPS again ? if not whats the process ?

Are you staying with the Air Force?
Or going Reserve in another branch?

You probably just need to go talk to a recruiter. The recruiter might just have to assign you to a unit and then that unit submit a voucher for a PHA to be performed to make sure you are up to date on everything. A recruiter would know what the process would be to pull you off the IRR and back into the active reserves.

i am not sure but i but its best to ask your nearest base or a recruiter

If I understand your post you were IMA, but are now IRR and have been so for 3 months and are now attempting to go Air Force Reserves? IF I understood you correct then, then it would boil down to hold long have you been on this contract and has it lapsed? IE when you signed up, did you do your complete 8 years? If you are still on your contract and have time, it is likely a matter of getting with a recruiter and explaining what you want. I have not experience with Air Force Reserves but Army it is a matter of getting assigned to a reserver unit. You may have to reclass/change jobs to do so.

A MEPS trip is not in order unless you got out of the military altogether. But things could have changed. Check with a recruiter.