Let \(K_{3}\) be a non-normal cubic extension over \(\mathbb{Q}\) , and let \(a_{K_{3}}(n)\) be the \(n\) -th coefficient of the Dedekind zeta function \(\zeta_{K_{3}}(s)\) . In this paper, we investigate the asymptotic behaviour of the type \( \notag \sum_{n\leq x}a_{K_{3}}^{2}(n^{\ell}),\) where \(\ell\geq 2\) is any fixed integer. As an application, we also establish the asymptotic formulae of the variance of \(a_{K_{3}}^{2}(n^{\ell})\) . Furthermore, we also consider the asymptotic relations for shifted convolution sums associated to \(a_{K_{3}}(n)\) with classical divisor function.