To animate a line graph in PowerPoint, you need to open the slide, draw the Graph add the labels and then animate the graph as explained here.

Almost any PowerPoint presentation would benefit from clever animation, and the Internet has an endless supply of animated templates ...

When presenting this to an audience as a slide show, I recommend starting with graph 1 on the screen, then, using the animation feature of PowerPoint fading in graph 2, and then fading in graph 3 ...