How do I setup and perform a mail merge in Pages?

I struggling to perform a custom mail merge. My goal is to print drawer labels for my parts organizer, using a Numbers file that contains two columns (fields): the **[name]** of each discrete component and its **[value]**. The mail merge pane, however, is blank with no available options for creating a data field. I suspect it can only be added by connecting to a data source first, but there's no option for it either. Unfortunately, every example I’ve found only demonstrates using Contacts as the data source, and they all rely on Pages built-in templates. While there are mentions of using Numbers files for mail merge, I can’t find instructions on how to link it to a Pages document. It seems like Pages’ Mail Merge functionality might be designed to work only with contact data, rather than supporting general-purpose custom data. Is this correct, or is there a way to accomplish my goal?