It's given that $210$ is $p\%$ greater than $30$. It follows that $210=\left(1+\frac{p}{100}\right)\left(30\right)$. Dividing both sides of this equation by $30$ yields $7=1+\frac{p}{100}$. Subtracting $1$ from both sides of this equation yields $6=\frac{p}{100}$. Multiplying both sides of this equation by $100$ yields $p=600$. Therefore, the value of $p$ is $600$.