convert vertical data to horizontal

Use a pivot table.

In column A you first need to fill the blank cells with the correct account ID: Select column A, hit F5 > click Special > Tick "Blanks" > OK > enter a = sign > hit the up arrow on the keyboard > hold down Ctrl and hit Enter.
Now there are no blank cells in column A and you can build a pivot table.

Select a cell in the data table, then click Insert > Pivot table > drag the Account ID to the row box, the Product to the column box and the Total to the values box.

If you want, you can then copy the pivot table and paste it to another sheet, using paste special > Values