Finitely generated module over formal power series can be transformed in a free module.

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If $M$ is a finitely generated $\mathbb{C}[[ t]]$-module, I have to show that there exists a $n \in \mathbb{N}$ such that $t^nM$ is a free $\mathbb{C}[[t]]$-module. I have no idea how I can start with this proof so any help would be greatly appreciated!