*square root symbol* y^3 multiplied by *square root symbol* y^3

The product of two radicals is equal to the radicand. The square root deletes itself.

So the result is y^3

√y³ * √y³ = (√y³)^2

(√y³)^2= y³

Final y³
Remember that when you're trying to find the root of a number times the root of the same number, it is equal to the root of the number squared, which cancels out.