How do I transfer my music now on my MACBOOK PRO

With macOS Catalina, your iTunes media library was migrated to Music, TV, Books, and Podcasts apps. Finder is now where you manage and sync content on your iPhone, iPad, and iPod touch.

For an overview of the changes in Catalina regarding media apps, see the article below.

What happened to iTunes?

https://support.apple.com/en-us/HT210200