I don't know what your question means, but 7 cubed is 343, so the cubic root of 343 is 7.

![\sqrt[3]{343} = 7](https://img.qammunity.org/2019/formulas/mathematics/middle-school/sx7on81h727rwchfmwgwf55knr92dhrhfo.png)
Exponent and root are inverse operations.
If you square 5 to get 25, then when you take the square root of 25 you get 5.
7^3 = 343, so the cubic root of 343 is 7.