The easiest and most direct way to find out whether or not your ex misses you is to ask him. Unfortunately, for most people, this is also the most intimidating way; however, simply talking with him is likely the quickest way to figuring out what's going on.  Be aware that, depending on the person, some people may not be honest about their feelings, especially if they are afraid that you are trying to hurt them. If you and your ex aren’t able to communicate without getting into a big fight, meeting up to try and have conversation about a topic like this may not be the best idea. Asking your ex outright seems scary, but it can save you a lot of confusion in the long-term — instead of spending time trying to interpret his silence or what, exactly, his use of that smiley emoji meant, you'll know flat-out if he wants to get back together. If he doesn't then you can begin the work of letting go and moving on and not waste your time on someone who no longer wants to date you. You can contact her via text or email, but the fastest way is probably just to call her. Keep your conversation as light and friendly as possible. Ask her if they’d like to meet up for lunch or coffee because you want to talk about something with her. Understand that she might refuse. If she does refuse to see you it’s a good sign that she doesn't miss you, or if she does, she isn't ready to see you yet. Try not to get angry. Instead, be respectful of her wishes. If this is the first time you are seeing each other since the break up the situation will probably feel a bit awkward. Take the initiative and try to keep the situation as light as possible. Ask him how things are going for him (e.g. with school or work), and let him know a few things that are going on in your life. Try to keep the conversation on light things and don’t just jump straight into talking about your relationship. This will help lighten the mood, and let him know that you aren’t trying to start a fight. If you are at a restaurant or cafe, and are ordering food and/or...

TL;DR in Indonesian:
Putuskan apakah bicara merupakan ide bagus. Hubungi dia. Usahakan membuat suasana tetap santai. Tunggulah saat yang tepat. Jujurlah kepadanya. Putuskan apa yang harus dilakukan selanjutnya.