Assuming you are full-time, most likely you will have 15 credit hours a semester. That's roughly 15 hours of in class time a week. The difference with undergrad is that your school will likely assign you, as a 1L, to a section, and your schedule is determined by the section. Everyone in the section is in the same classes, except maybe a writing or research class.
But most people say allow 2-3 hours of prep/study time for each class, done before the class. So you could be up to 45-60 hours if you include class and prep/study time.