Although I can't see your excel file, but I appreciate if you try to define by another name to continue exercise, and in real project, you can ask SSA or LSA to advise.
Or if you mean that you can't find "Data Type" in Data Explorer, then 1. Open Data Explorer menu by clicking right up side triangle 2. Select "Show or hide existing data types" 3. Check "View all" 4. Check your defined - invisible - Data type