I'm 28 so I have a pass, right?
Not necessarily. The Detroit Department of Transportation (DDoT) does not hand out passes automatically. Users of the public transportation system in Detroit have to affirmatively buy passes, even users who are 28 years of age. So unless you bought a pass then no, you wouldn't have one.
Look in the upper right-hand drawer of your desk, beneath all those old checking account statements. Maybe you'll find your pass there, if indeed you purchased one. Or it could be in the kitchen drawer with all those extra batteries. If you do need to buy another pass, call the DDoT at (313) 933-1300; they'll be able to tell you the most convenient place where you can get one. Because you are neither a senior nor (presumably) disabled, the cost of a monthly "GoPass" for you would be $47.00. (You can buy a weekly GoPass for $14.40, and a 5-day pass for $14.00.) You will need to carefully assess your public transportation needs in order to buy the pass that will be the best value for you.
Please note that both your Yorkshire terrier and that fox who's squatting on your property are allowed to ride the bus with you, on the condition that they are trained service animals.
If they are not trained service animals, they will still be able to ride with you if you sneak them onto the bus. You can pull that off if your dog and the fox are each wearing sunglasses and a Detroit Tigers T-shirt and ball cap. And tiny flip-flops. (But only on their hind feet so that they won't attract attention.) And you'll have to pay their fares.
If you have further questions regarding your pass, please call the Detroit Department of Transportation at the number I cited above. Of course, questions about sunglasses, Detroit Tigers T-shirts and ball caps, and tiny flip-flops may be posed right here in this fine clothing forum.