You need a decimal tab stop; you can select multiple cells to set a tab stop for all cells at the same time. A decimal tab stop within a table doesn't require you to add a tab character manually. Word immediately moves the item to the location of the tab stop.
You can access the Tabs dialog box from the Paragraph dialog box, which you can display by clicking the dialog launcher button in the Paragraph group on the Home tab (the dialog launcher is the little arrow at the bottom of the Paragraph group; see the screen shot you posted earlier).
All this is discussed in the article at
http://word.mvps.org/faqs/formatting/SettingTabs.htm.