As per the question it is given,

Radius of the cylindrical portion (R) $=20m$

Height of the cylindrical portion $\left( {{h}_{1}} \right)=4.2m$

Height of the conical portion $\left( {{h}_{2}} \right)=2.1m$

Then, we all know that formula of

Volume of the Cylindrical portion $\left( {{V}_{1}} \right)=\pi {{r}^{2}}h_{1}^{{}}$

${{V}_{1}}=\pi {{\left( 20 \right)}^{2}}4.2$

${{V}_{1}}=5280{{m}^{3}}$

Now, the volume of the conical part $\left( {{V}_{2}} \right)=1/3\times 22/7\times {{r}^{2}}\times {{h}^{2}}$

${{V}_{2}}=13\times 22/7\times {{20}^{2}}\times 2.1$

${{V}_{2}}=880{{m}^{3}}$

Thus, the total volume of the tent (V) $=$ volume of the conical portion $+$ volume of the Cylindrical portion

$V={{V}_{1}}+{{V}_{2}}$

$V=6160{{m}^{3}}$

Therefore, volume of the tent is $6160{{m}^{3}}$