That dinosaurs are not mentioned in the Bible does not mean Christians do not believe in dinosaurs. The Bible is simply a record of the faith history of one nation with their God, Jehovah, who promises them, "I will be your God, you will be my people".
The Bible explains creation this way:~ The two accounts of creation in Genesis are a spiritual truth; God made the world, and placed man in the centre of creation as his greatest creation. The Bible gives a spiritual truth about creation. It does not give the facts about evolution.
We can look to the descriptions of dragons in ancient legends for evidence that men encountered dinosaurs in the flesh before they encountered them as fossils. That the Bible doesn't mention them specifically simply indicates that they weren't a factor in the lives of the people of that time and place. It doesn't mention kangaroos, either--they weren't relevant. It is possible the Behemoth and Leviathan mentioned in the book of Job--which seems to be from a time a few hundred years following the flood--are describing a land and a sea creature we would think of as dinosaurs. The descriptions do not match well with any living creatures of our day.