Help with mileage reimbursement law

Primary job location is 6 miles from my house. Was required to attend a meeting at a location (that I do not work shifts at) that was 20 miles away. I believe I should be reimbursed for 28 miles at the rate of 65.5 cents. I asked my manager how we submit for reimbursement and he was like… what is that? I said it’s a law and he rolled his eyes. Anyone experience this? How do I get this taken care of. It’s not the $18 it’s making sure my employer is following labor laws.

Not sure if it matters but this job is part time.