I'm not sure what "7.0" is but first let's locate your icons, then I'll tell you how to edit them.
To locate where your icons are, you can open a terminal and type:
locate icons | more
This will produce a lot of output, but it will show you every folder on your machine named "icon". Icons should be in there. To find something specifically from your menu, go to System -> Preferences -> Main Menu. This shows me a list of all the entries on the menus and their icons. It looks like this:
Then click on one of the applications and right-click. You should get a sub menu. Click "Properties" and something like this should appear:
Click on the icon and it should show you some icons. There will be a path at the top of the icons and it should look like this:
In this instance the location of the icons is in /usr/share/pixmaps. Now, to edit the size of these icons, you'll need an image editing program. You should have Gimp installed. Start Gimp from a terminal with root permissions, navigate to the icon file, and open it. You can re-size the icon by selecting the "Image" Menu, then "Scale Image" from the sub-menu. You'll see some numbers appear. Increase the value of these numbers, click apply, and you'll see the image expand. Pick the size that you want and save the icon.