I am assuming that you opened the exported CSV file on Microsoft Excel. The missing leading zeros is due to Excel's default behavior.
This can be overcome by using the the data import wizard on Excel. You can use this by following the steps mentioned below:Step 1:
Under the file options - choose the import option.Step 2:
Bring in the exported CSV file after choosing the CSV option on the import WizardStep 3:
Choose the desired (Delimited or Fixed Width) option and then hit the Next ButtonStep 4:
In this case, choose the desired delimiterStep 5:
Select the Text Option - in order to keep the leading zeros in your data and hit finishStep 6:
You will now see the leading zeroes in your data.
I hope this helps!