Hi @fernandac322631 ,
I share with you an Adobe doc link.
You can do a workflow in order not to touch the file, following the next steps regarding activities:
-Load file activity: It will load your file into a temporary table.
-Enrichment: Here in the Additional data tab it will be necessary to ad a calculated field to transform the 17 character field by extracting the required 13 characters.
-Creating the calculated field: Here we can manage two options, using substring function or doing a JavaScript.
-Map the field correctly to the target table through an Update Activity.
-Test it to be sure, that works correctly.
Regards,
Celia