Answer
See below
Work Step by Step
We have:
$$A=SDS^{-1}$$
then $$A^2=(SD^2S^{-1})=(SDS^{-1})(SDS^{-1})$$
For $m \gt 2$, we obtain $A^m=SD^mS^{-1} \\
A^{m+1}=A.A^m=(SDS^{-1})(SD^mS^{-1})=SD^{m+1}S^{-1}$
Hence, for every $k=1,2,3.... \rightarrow A^k=SD^kS^{-1}=$