I'm 16 years old my penis is kind of small, so many ideal few cm to 10 cm?

Maybe not so: A lot of laymen make a false measurement. There is a fat pad called the "Mound of Venus" (go figure) and you are measuring from the top the pad to your penile tip. Instead, lie down in bed and with your second and third fingers press down on either side of your penile shaft and you'll notice it'll elongate.you just started measuring at the wrong starting line! Good luck!