Hi there!

Adding a file extension to the end of the contents of every cell in column A is actually quite simple. Here's how you can do it:

1. First, insert a new column next to column A by right-clicking on the column A header and selecting "Insert" from the drop-down menu.
2. In the new column B, enter the formula
   Formula:

   "=A1&".jpg"" 

   in cell B1. This will concatenate the contents of cell A1 with the file extension ".jpg".
3. Copy the formula in cell B1 by selecting the cell and pressing Ctrl+C on your keyboard.
4. Select the entire column B by clicking on the column header.
5. Right-click on the selected cells and choose "Paste Special" from the drop-down menu.
6. In the "Paste Special" dialog box, select "Values" and click "OK". This will replace the formulas in column B with the actual values.
7. Finally, you can delete column A if you no longer need it.

That's it! Now every cell in column B should contain the original contents of the corresponding cell in column A, followed by the file extension ".jpg". Let me know if you have any questions or if there's anything else I can help you with.