How do you change the index of a radical?
I am not sure what you mean but
square root is a power of (1/2)
$$\\\sqrt[2]{x}=x^{1/2}\\\\ \sqrt[3]{x}=x^{1/3}\\\\ \sqrt[4]{x}=x^{1/4}\\\\ \sqrt[5]{x}=x^{1/5}\\\\ \sqrt[6]{x}=x^{1/6}\\\\ etc$$