To unhide the column D, for example, you need to select columns C and E together, right-click on either column’s letter, and click on “Unhide.” The easiest way to unhide all rows and columns is pressing Ctrl + A to select all of them, right-click on any row or column, and also click on “Unhide.”
Hide Rows, Columns, and Sheets
The Format menu lets you hide and unhide rows, columns, and sheets with a single click.
In the “Home” tab on top of the window, find the “Cells” category and click on “Format.” This will open a dropdown menu.
Go to “Hide & Unhide” and see if you want to hide a row, column, or sheet. Naturally, hiding any of these with just a single cell selected hides the entire row or column that contains this cell.
Note: The unhide actions reveal all previously hidden rows, columns, and sheets.