iTunes does not show my iPhone when I connect it to my Mac what i should do ?

You mention "brand new Mac", is it running macOS Catalina?

On mac OS Catalina, your iTunes media library is now available in the Apple Music app, Apple TV app, Apple Books app, and Apple Podcasts app. And Finder is where you can manage and sync content on your iPhone. See What happened to iTunes? - Apple Support

----------------------------------------------------------------------------------------------------------------

If you are using an older mac OS (not Catalina), then follow these steps:

If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support

Does it fix your issue?

Also under section: If you use a Mac, what were the results of step 4.

Do you see iPhone?

yes