Even though there is no word for hell in the Old Testament, the judgment of God is mentioned clearly in the Old Testament.
"Your hand will find out all your enemies;
Your right hand will find out those who hate you.
You will make them as a fiery oven in the time of your anger;
The Lord will swallow them up in His wrath,
And fire will devour them." (Psalm 21:8-9)
"Those who hate the Lord would pretend obedience to Him, and their time of punishment would be forever." (Psalm 81:15)
"Many of those who sleep in the dust of the ground will awake; these to everlasting life, but the others to disgrace and everlasting contempt." (Daniel 12:2)
It is not possible for the blood of animals to atone for the sins of the soul. That is why Messiah came to earth to atone for humans Himself. The perfect Son of God died in place of the unrighteous so that we can be made perfect through faith in Him. Those who believe in Him [Jesus] will not end up in hell.
"I will tell of the decree:
The Lord said to Me, 'You are My Son;
today I have begotten You.
Ask of Me, and I will make the nations Your heritage,
and the ends of the earth Your possession.'" (Psalm 2:7-8)
"Therefore the Lord Himself will give you a sign. Behold, the virgin shall conceive and bear a Son, and shall call His name Immanuel." (Isaiah 7:14)
"But He was pierced through for our transgressions,
He was crushed for our iniquities;
The chastening for our well-being fell upon Him,
And by His scourging we are healed.
All of us like sheep have gone astray,
Eash of us has turned to his own way;
But the Lord has caused the iniquity of us all
To fall on Him." (Isaiah 53:5-6)
See Isaiah 52 and Isaiah 53.
https://www.bible.com/bible/100/ISA.53.NASB1995
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Jesus mentioned Hades in the gospel of Luke 16:19-31.
He told the story of a rich man who went to Hades and was tormented by fire, because during his lifetime he did not listen to God or help his fellow man.
See: https://www.bible.com/bible/100/LUK.16.NASB1995
From these verses, you can see that hell exists. But God sent His Son so that we can have eternal life through Christ:
"For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life." (John 3:16)