One reason I believe but have some doubt about the bible is because man found dinosaur fossils and other things that confirm the Earth is older than the bible says. So if the bible is true, why doesn't it mention Dinosaurs? If it's true, then why does it say the earth is only thousands of years old?
Finding an animal fossil does not prove the age of the earth. Fossils prove that an animal died and got buried very quickly in mud and turned to fossil. Fossils do not take millions of years to form. Dinosaurs are simply extinct animals, same as anything else.
The Bible certainly mentions Dinosaurs.
Genesis
21 So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it
24 Then God said, “Let the earth bring forth the living creature according to its kind: cattle and creeping thing and beast of the earth,
each according to its kind”
Job 7:12
12 Am I the sea, or the monster of the deep,
that you put me under guard?
Psalm 148
7 Praise the Lord from the earth,
you great sea creatures and all ocean depths,
Jer. 51:34
Like a serpent he has swallowed us
and filled his stomach with our delicacies,
and then has spewed us out.
Job 40
“Look at Behemoth,
which I made along with you
and which feeds on grass like an ox.
16 What strength it has in its loins,
what power in the muscles of its belly!
17 Its tail sways like a cedar;
the sinews of its thighs are close-knit.
18 Its bones are tubes of bronze,
its limbs like rods of iron.
19 It ranks first among the works of God,
yet its Maker can approach it with his sword.
20 The hills bring it their produce,
and all the wild animals play nearby.
21 Under the lotus plants it lies,
hidden among the reeds in the marsh.
22 The lotuses conceal it in their shadow;
the poplars by the stream surround it.
23 A raging river does not alarm it;
it is secure, though the Jordan should surge against its mouth.
24 Can anyone capture it by the eyes,
or trap it and pierce its nose?
Job 41
“Can you pull in Leviathan with a fishhook
or tie down its tongue with a rope?
2 Can you put a cord through its nose
or pierce its jaw with a hook?
3 Will it keep begging you for mercy?
Will it speak to you with gentle words?
4 Will it make an agreement with you
for you to take it as your slave for life?
5 Can you make a pet of it like a bird
or put it on a leash for the young women in your house?
6 Will traders barter for it?
Will they divide it up among the merchants?
7 Can you fill its hide with harpoons
or its head with fishing spears?
8 If you lay a hand on it,
you will remember the struggle and never do it again!
9 Any hope of subduing it is false;
the mere sight of it is overpowering.