I need a ringtone for my iPhone Pro

Go to Settings -> Sounds & Haptics -> Under Sounds and Haptic Patterns, tap any sound.

Or buy ringtones from the iTunes Store, see -> Use tones and ringtones with your iPhone, iPad, or iPod touch

Use tones and ringtones with your iPhone or iPad - Apple Support

I do not have a ringtone.

Did you follow the instructions listed in this thread?