Turn Off the Sound Effect in the beginning of my macbook's start

If the information at the bottom of your post is accurate ie you have a MacBook Pro 13" running macOS 10.15 - the ability to turn off the startup chime requires macOS 11 (Big Sur) and above.

febrinap wrote:

I read the instruction, but there is no “Play sound on startup” to set in the Sound Effects pane. Where to find it?

?

>System Preferences>Sound

Turn the Mac startup sound on or off - Apple Support