As I'm sure you recall, Jurassic Park is about a scientist who clones dinosaurs from DNA preserved in amber.
Although the film was entertaining, and the special effects spectacular, it contained several scientific inaccuracies. Cloning dinosaurs might be an intriguing idea, but scientifically speaking it's not possible.
We can clone sheep and other animals, right? So why not dinosaurs?
To put in different terms, cloning a dinosaur is theoretically possible, but it's not like cloning a sheep.
It has to do with how cloning works. In nuclear transfer cloning, a nucleus from the animal to be cloned is inserted into an egg with its nucleus removed. The nucleus contains most of the genetic material of eggs and other cells. If things go well, the egg with its new nucleus forms an embryo that starts to divide and mature. After a few days it's transferred to a surrogate mother.
Why not do that with dinosaurs or other extinct animals like wooly mammoths?
The problem is that we don't have well preserved DNA from dinosaurs and wooly mammoths. Millenia of freezing and thawing, and other processes break up most of the DNA. Even if we did find usable dinosaur DNA, finding a surrogate mother similar in size and biology to a dinosaur would be difficult, to say the least. Crocodile or ostrich eggs might be as close as we could come.