Step 1: Change the reporting verb. Since the direct speech is a question, the reporting verb 'said' changes to 'asked'.
Step 2: Remove punctuation. The quotation marks and question mark are removed.
Step 3: Change the verb tense and pronoun. The verb 'can' changes to its past tense form 'could'. The pronoun 'I' changes to 'he' to match the subject.
Step 4: Change the sentence structure. The interrogative structure ("Where can I...") changes to an assertive structure ("where he could..."). This gives the final sentence: "He asked where he could get a book."