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# I am having trouble mapping my source file columns. What are the column headers/index? What do the various attributes do?

**Answer**:

The column header is the content of the first or topmost row in the source file. 

The leftmost column in your file is indexed 1 and the column after is indexed 2. 

Your inputs in the **Source Mapping Column** section should contain the column header or the column index in your source file. Please note that the column header must match exactly with the one in your source file.

*   Prefix & Store Prefix: This strips the source file's leading product identifier by what is the input in the column. For example, if SKU in the source file is **ABC1001121** and the input is **ABC** in the input, **1001121** will be matched against the SKUs in your store.  
      
*   The product key, quantity key, selling price key, barcode key: Column header of product identifiers or column index. For example, a column header for the product key would be **SKU,** and the quantity key would be **Qty**.  
      
Ensure that the columns are properly matched by the column header or by the column index. 

We strongly encourage the use of the column index as this method is safer than using column headers.