We can assume that our understanding of “belief” today is different than what most of the Bible writers had in mind. We often think of belief as “accepting that something is real” (such as a child believing in Santa Claus). This is not the type of belief that is discussed in most places in Scripture.
This question can be answered very clearly with John 3:36 which states: "He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him.” (NASB).
In the book of John, “belief” is more than just accepting that Jesus is real”. It involves “obedience”. In fact the word in this verse for “does not obey” is a word that means “being subject to”. To truly believe, one must subject themselves to the authority and rule of Jesus. True belief involves obedience and subjection.
With this understanding of the word “belief”, John 3:16 has a much deeper meaning. "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”
Eternal life awaits those who subject themselves to Jesus.