Let $K \neq \mathbb{Q} $ be a finite extension of $\mathbb{Q}$. For a given integer $n$, how to construct an unramified extension of $K$ of degree $n$ ?

EDIT: If not then under what conditions on $K$, the above construction is possible ? Is it true if we take a local field i.e. $K$ is a finite extension of $\mathbb{Q_p}$ for some fixed prime $p$ ?