I'm using Commcare for a longitudinal study. I created cases via Excel import that has identifying information for each case and used an External ID number. However, when I now want to export the data from my questionnaire (which is a follow-up form), I can't figure out how to link my external ID to the follow-up form data when I export it. How can I export the identifying information from the case registration with the follow-up form data. It is critical that the unique identifier in the case registration export along with the questionnaire (follow-up form) data.