You need to change your view often in PowerPoint, and you've always done it easily by using buttons. That hasn't changed. The buttons for Normal, Slide Sorter, and Slide Show views are still there — they've just moved from the lower left of the window to the lower right.
They're part of a new toolbar that includes a zoom slider and a button that refits the slide to the window after you've zoomed in or out.
Remember There's a View tab, too, and it has the whole smorgasbord of views — Notes Page view, Master view, a list of other open presentations, and so on.