1. Go to Analysis > Information Library
  2. Click Add an ad-hoc query
  3. Select the source view of constituents and click OK. 
  4. From the middle column, drag "Is individual" to Include records where. Set this equal to Yes. 
  5. From the middle column, drag "First Name" to Include records where. Set this to be blank.
  6. Add any additional information to help with data clean up to Results Fields to display. 
  7. Save your query to access later.