Enter the formula in the upper right-hand cell. Copy it. Then select 3x500 cells, and paste.
Enter the formula in the upper right-hand cell. Select the cell. Grab th elower right-hand corner of the cell (you will see a little grip, and when you hover the cursor changes to a black cross) and drag to the right as many columns you need. Release the grip. Then grab the grip again, and drag down as many rows as you need, and release.