where is my music

If you have transferred to iPhone, it will be under Music App on iPhone.

Listen to music and more in the Music app - Apple Support

https://support.apple.com/en-us/HT204951

How was it transferred to the computer exactly?

Where was it stored on the computer?

How was it then transferred to the iPhone exactly?

What steps did you follow?

If you used iTunes to transfer the music to the iPhone, then yes, it should be inside the Music app.

Otherwise, provide details and context, and someone may be able to help.

You need to explain the issue in more detail, before anyone can help you.

Writing an effective Apple Support Community Question