Here's how you can replace all numbers greater than 0 with 1 in Excel:

1. Select the range of cells that you want to convert to presence/absence format.
2. Right-click on the selected cells 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 following format code:
   Formula:

   0;-0;0; 

5. Click "OK" to close the dialog box and apply the new format to the selected cells.

This format code will display all positive numbers as 1 and all negative numbers as 0. So, any value greater than 0 will be displayed as 1, effectively converting your data set to presence/absence format.