By default, all numbers entered in your spreadsheets use the Standard number format. This Standard format is also known as the General number format and shows numerical entries with no decimal places and no special formatting (such as commas or dollar signs).
While the Standard, Currency, and Percentage formats are easily accessible from the Object toolbar, the other formats available for your numbers are found in the Cell Attributes dialog box.
Select the cell or cells that you wish to assign a number format to.
Select the Format menu, then select Cells. Or, right-click the selected cell or cells and select Format Cells from the context menu. The Cell Attributes dialog box appears ...