SAP upload file (import) ABAP development

Using transaction code FF_5 i upload a file from external system to SAP ECC, recently the file format has changed. The first column of the old notepad import file contain a 6 digit branch code, now the new file contain 12 digits, 6 of this digits being zeros. On upload of the new file SAP is throwing an error on the characters.
I require an ABAPer to adjust the first column to accept the new data format.