According to a show is watched, people believed in multiple God’s for a long time until many years after the earth was formed; then, the Jews started talking about one God. If this is true, how did God tell the Jews about one God and when? If this is true, did the pagans (before the Jews talked of one God) have a chance to know about God? Did God find a way to show himself to them years before the Jews started talking about God? ‘
First of all, there were no people for about the first 4.5 billion years after the earth formed. People have only been around for a few tens of thousands of years. No one knows exactly what all people believed in the distant past. In fact we know extremely little about what people believed thousands of years ago, at least from archaeological evidence. We have to speculate. You should take the confident statements you hear in such shows with a big grain of salt. (Of course you might want to take what I say with a grain of salt as well, but I hope to be more cautious in my conclusions)
Having said this, the evidence leads to a broad conclusion, which is that most primitive people had a religion which could broadly be defined as animism. They saw "spirits" in rocks, trees, animals, streams–in both animate and inanimate objects. Later, more sophisticated societies arose which moved more in the direction of polytheism–believing an a kind of pantheon of personal human-like gods on a higher plane of existence. Polytheism was the brand of religion most common in the Near East at the time Judaism arose about 1500 BC or so.
Now that I have given an extremely simplified and overly simplistic background to what we DO know, this simplification does not explain all the religious beliefs of all people. By 1500 BC, polytheism in India was beginning to evolve into a mixture of polytheism and pantheism–the view that God is impersonal and that he fills the universe. I believe that we ought to assume that there were a very wide variety of religious beliefs in the ancient world.
Add to this the fact that there were believers in the one true God in the ancient past. Noah believed in the one true God, as did Job. Neither were Jewish. According to the biblical picture, there have always or nearly always been some people who believed in a single God who created the universe and who created us humans. The Bible pictures these "patriarchs" receiving knowledge of God directly by him speaking to them. This certainly was the case with Noah and his sons. We are less sure with Job how he knew of the God of Israel. Possibly God revealed himself to this partiarch directly, or perhaps Job learned about God from those who came before him. We know that Melchizedek, a contemporary of Abraham believed in the one God as well. Abraham came from a family, all of whom, it appears, believed in this same single God. His father Terah, as well as his brother Laban believed in this same God. God spoke to Abraham directly. How he spoke to others who believed in God at the time, we are not sure, but it is possible that God communicated with and spoke his will to some of these patriarchs as well.
It is possible that there have been believers in the true God in various parts of the world, on every continent. However, such knowledge has not come down to us. We are not justified in assuming either that such believers did or did not exist, but it certainly is possible. Virtually all ancient people have left us no record at all. The Bible is really unique as a consistent story of a people which stretches back so far in time.
So, we have a few hints in Genesis of a number of believers in the God who the Jews eventually accepted as their God–the real one! This evidence stretches a thousand years before Moses and perhaps many thousands of years before him, to include Job, Noah Melchizedek, the extended family of Abraham and probably many more we do not know of.