You need to read publication 463, especially chapter 4, and publication 587.
https://www.irs.gov/forms-pubs/about-publication-463
https://www.irs.gov/forms-pubs/about-publication-587
Most of your mileage could be work mileage if your home was your "principle place of business". Your home can be your principle place of business if that is where you do your administrative work (making appointments, calling client, keeping records, and so on). You don't have to actually take the home office deduction to call your home your principle place of business.
