First of all, you can ask yourself whether you really miss him or just want to find a topic to chat with him. If you really miss him, you can tell him how you feel. But if you just want to find a topic to chat with him, just tell him what you think.
Secondly, you can consider whether your relationship is healthy and whether you have enough time and opportunities to get along. If your relationship is already very close, you can tell him that you miss him and ask him if he misses you too. But if your relationship is not close enough, you can tell him how you feel, but at the same time you should respect his feelings.
Finally, you need to make sure that your answer is true, not just a lie that meets his expectations. If you feel uncertain or unsafe, you can tell him how you feel, but at the same time you should keep an open and respectful attitude.