To clear the cells, I clicked the area between cell A, and 1 to highlight all of the cells. Afterwards, I went to Home–>Clear—>Clear format to remove the apostrophe.
To edit/fix the cells, I selected the last group,i.e. BX to highlight all of the cells in that column. Then, I dragged the arrow to the left to get all of the other cells highlighted. Afterwards, I clicked the error button to convert the text to numbers.