1998 Ford Mustang exhaust

This is a case where the least expensive and quickest solution is to visit an exhaust specialty shop. They will have the right hanger in stock and they'll inspect the rest of the exhaust system. By the time a hanger rusts or breaks off, it's usually the time other parts are deteriorated. They will take you under the car and show you any other parts that need to be replaced and why. Beware of the large chain franchises. They can do a perfectly fine job, but many of them pay their mechanics a commission on the parts they sell so there's a huge incentive to sell you things that are marginal or you may not need yet.

You will also get to avoid laying on the ground to fix this and getting rust and scale in your eyes. If you still want to pursue the repair yourself, visit any auto parts store. They will have a listing for all of the parts for your exhaust system, including the tail pipe hanger. Their very first question is going to be which engine you have.