Finite Abelian Group Proof

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Show that a finite abelian group is not cyclic if and only if it contains a subgroup isomorphic to $\mathbb{Z}_p \times \mathbb{Z}_p$ for some prime $p$.

I'm not sure what to do. Any proofs or hints are greatly appreciated.

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Hint: If $a^n=b^m=1$ and $(n,m)=1$ (i.e. the orders are coprime) what can you say about the order of $ab$? Try finding an element of maximum possible order, and considering the possibilities that arise.