To display the number 1 as 01 or 001 in an Excel cell, you can use the custom number format feature. Here's how:

1. Select the cell or range of cells that you want to format.
2. Right-click on the selection and choose "Format Cells" from the context menu.
3. In the Format Cells dialog box, select the "Custom" category.
4. In the "Type" field, enter the desired format code. For example, to display the number 1 as 01, enter
   Formula:

   "00" 

   (without the quotes).
5. Click "OK" to apply the format to the selected cells.

If you want to display the number with leading zeros for all values in a column, you can apply the same custom format to the entire column by selecting the column header and following the same steps.

Note that the custom format only affects the way the number is displayed in the cell, not the actual value of the cell. So, if you use the formatted cell in a formula, the formula will still use the actual value of the cell, not the formatted display value.