You might have seen the Jurassic Park movies. In the original feature film, based on the Michael Crichton novel, scientists use DNA preserved for tens of millions of years to clone dinosaurs. They run into trouble, however, when they realize that the cloned creatures were smarter and fiercer than expected. Could we really clone dinosaurs?
In theory? Yes. You would need:
A well-preserved source of DNA from the extinct dinosaur, and
A closely related species, currently living, that could serve as an egg donor and surrogate mother.
In reality? Probably not.