Correct Answer: Harry told me not to wear that expensive watch to school.

Solution : The fourth option is the correct choice.

The steps of conversion are as follows:

• The reporting verb "said" is changed to "told".
• The conjunction "to" is followed by the infinitive form of the verb in case of the imperative sentence.
• There would be no change in the tense since the sentence is an imperative sentence.
• The adverb "this" is changed to "that".

Therefore, the correct answer is: " Harry told me not to wear that expensive watch to school".