Radical expressions are written in the form [tex] \sqrt[n]{x^{r}} [/tex].
To convert them into a radical exponent, you just take n and r, and put them into this fraction form: [tex] \frac{r}{n}[/tex].
For example:
[tex] \sqrt[3]{x^{2}}=x^{ \frac{2}{3}
[/tex]
Hope this helps!