formatting column as text

You could just do a custom numeric format on that column, with something like "000000000009", that would be the simplest.

Or you could could create a text version in another column using a formula like =TEXT(A2,"000000000009"), and if desired then copy by value back to the original column.

If you really do want to change the existing cells to text with no formatting changes, or copying of cells, then you would need a VBA macro to do that, but that feels like more work / complexity than needed.

You can use the "Text to Columns" option on the Data tab to change the number to text. Select the column you want displayed as text. Then click the "Text to Columns" option. Select "Delimited" for Step 1, unselect all delimiters on Step 2, and finally select "Text" on Step 3.

If you are doing it

... so it left aligned

Then why not simply change the cell alignment to left?

Shaune, your suggestion work for that moment, it does look right but when I save the file back as CSV(because that is the original format) and open the file again, UPC column is back to scientific notation look.

thanks Sqib, That will only be good in screen . Save it and open it, it's back to original.