I worked for FedEx. I delivered packages with my car. I am not self-employed or an independent contractor. Can I write off my mileage? I drove over 9000 miles for them.

Do you get a W2 or a 1099NEC for it?  Sorry you can't deduct expenses or car expenses if you are a W2 employee.  

Are you a W-2 employee?

Sorry---W-2 employees cannot deduct job-related expenses on a federal return.  Job-related expenses were eliminated as a federal deduction for W-2 employees by the tax laws that changed for 2018 and beyond.  Your state tax laws might be different in AL, AR, CA, HI, MN, NY or PA.

If you live in a state that lets you deduct job-related expenses, the information will flow from your federal return  to the state return, so enter it in Federal>Deductions and Credits>Employment Expenses>Job-Related Expenses

Do you work for FedEx, or a FedEx subcontractor? Either way, your employer should be reimbursing you for mileage or paying you a mileage allowance or it's included in your hourly rate.  

As others have said, W-2 employees don't get to deduct mileage (or any other job expenses), unless the "statutory employee" box is checked on the W-2.