It is given that,
Radius of metallic sphere $=R=10.5cm$
So, its volume $=4/3\pi {{R}^{3}}=4/3\pi {{\left( 10.5 \right)}^{3}}$
We also have,
Radius of each cone $=r=3.5cm$
Height of each cone $=h=3cm$
And, its volume $=1/3\pi {{r}^{2}}h=1/3\pi {{\left( 3.5 \right)}^{2}}\left( 3 \right)$
Thus,
The number of cones $=$ Volume of metallic sphere/ Volume of each cone
$=4/3\pi {{\left( 10.5 \right)}^{3}}/1/3\pi {{\left( 3.5 \right)}^{2}}\left( 3 \right)$
$=126$