Excel's Format Cells dialog box launcher icon in the Number group of the Home tab on the ribbon. The Sample area of the Number tab in Excel's Format Cells dialog box.

Click on the dialog box launcher in the Number section, the small arrow that points down and to the right at the bottom right corner of the section. This brings up the Format Cells dialog box with ...

Press CTRL + 1 on your keyboard, then select Number. Right-click the cell or cell range, choose Format Cells, then select Number. Click the dialog box launcher, and then choose Number.

Click "Close Master View" to return to the Normal view. Now, click File > Save As > Browse—or press the Microsoft PowerPoint keyboard shortcut F12—to launch the Save As dialog box.