Merging previously purchased music with 2 different apple id’s
I spoke with a tech support person this morning and told him I wanted to get back the apple music purchases I lost when I changed my Apple ID ... without losing anything from my new account. In other words, I want to merge all my music onto my new iPhone. He said he would send me a link explaining how to do that and the link does not explain it. When I tried to sign out from my new Apple ID, it said I would lose all my stuff on this phone. How can I merge previous purchases onto my new iPhone without losing anything? Please help
iPhone 8, iOS 12