You can’t do this with CSS, you’d have to edit the SVG element, particularly the viewBox
attribute. That attribute defines the coordinate system for the <path>
(a rectangle that goes from upper left to lower right). The bigger the rectangle, the smaller the path. The general syntax is:
viewBox="start-x start-y end-x end-y"
This would be an example how to center the folder icon:
<svg xmlns="http://www.w3.org/2000/svg" viewBox="-8 -5 37 35" width="45" height="45">
You can play with the values until you get the result you want for each icon.