(I am assuming you are asking no of states in DFA).
The correct answer would be 3. Minimum number of states in FA will be 3.
To solve this kind of problem first generate the set from given regular expression.
${(ab)}^{*}$ = $\{ \epsilon, ab, abab, ababab, .... \} $
Now see, $\epsilon$ is present in the set then first state will be final state. Second is $(ab)$, if you create FA to accept this string then it will need 2 more states. After this, think of each and every states that what happens if there is an $(a||b)$ will arrive. Make transition for that. These transitions may leads to create some more states. But this is how you can solve this.