What is Aliyah?
Correction you won't necessarily have to serve 3 years. It depends on many factors: the day of your arrival to Israel, your age, your health profile and your marital status on your draft day. When the time comes, your Shaliach will help you with all of that kind of information. If you are a woman, you do not have to serve once you've made Aliyah passed your 17th birthday.