Hi Ryan,
Thank you for posting your query in our community.
About how to delete every column with a cell that contains specific letter, you can try the following steps:
Select all the cells in the table.
Open Find and Replace window by using the Ctrl + F keyboard shortcut.
Click Find All, and immediately after that Ctrl + A.
Click Close to close the window.
With the cells selected, right-click to open the Delete window.
Select Entire column and press OK.
As you can see, all cells containing the word “delete” are removed.
About how to delete every third column, you need to add a help row first and enter MOD() formula like below.
Then select this entire row.
Open Find and Replace window by using the Ctrl + F keyboard shortcut.
Click Find All, and immediately after that Ctrl + A.
Click Close to close the window.
With the cells selected, right-click to open the Delete window.
Select Entire column and press OK.
Best regards,
Jazlyn