All My Music Mixes are Gone from my Iphone

Last time my iPhone updated, all my mixes disappeared. I have made a summer mix each year since 1995 and my mixes from 2010 to 2023 were on my phone. They were all made from songs I purchased from iTunes and/or added from my own purchased CDs. How do I get them back; this loss represents many hundreds of dollars and many hundreds of hours making the mixes. I want them back.