Are you a W-2 employee?
-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
If you are self-employed you can enter your mileage or other business expenses on your Schedule C.