How to get my previous purchases from my old apple ID into my new apple ID?

I purchased a new iphone today. I was able to get some of my songs back into my device but apparently not all of them. I have two apple ids but I don't use the old one anymore. So when I signed in the old apple ID, i got the songs from that account and that was great BUT not the songs from the new apple ID. This happened to me before when i was trying to transfer the songs onto the previous iphone i had and I had to wait 90 days. I don't want to go through that process again. Is there a way to be able to get my old songs onto my new apple ID?

I had All my songs on the previous phone and I don't remember how that even happen

Previous Phone: 4,177 songs
New Phone I have now: 255 songs

Added (1). I used my iphone to sign in and out of my apple IDs

Your purchases are permanently linked to your apple id. You can't transfer purchases from one apple id to another. You should have reused your old apple id
You could however log into iTunes on a computer with your old apple id, all your old songs should appear if you purchased them through iTunes, then export the songs onto a USB
You can then log in to iTunes with your new apple id and import the songs from the USB. You could then sync your iPhone with iTunes and your songs should be copied across

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