how do you make icons auto adjust in Finder when resizing the window

I just reformatted my computer becuase it was having issues. Before I reformatted the icons in the Finder window would move by themselves so I could always see them when I resized the window. Now, they don't do it anymore. Everytime I resize the Finder windo I have to click "clean up" or "arrang by" in order to see them all again. How do I get them to automatically adjust again?

Thank you,

Crystal