Which prophecies does Justin Martyr claim predict Jesus' Advent? Please identify them

In his First Apology Justin Martyr writes : > We find it also predicted that certain persons should be sent by Him into every nation to publish these things, and that rather among the Gentiles [than among the Jews] men should believe in Him. And He was predicted before He appeared, first 5000 years before, and again 3000, then 2000, then 1000, and yet again 800; for in the succession of generations prophets after prophets arose. Please identify the predictions he refers to (prophet, document, passage): 1. that certain persons should be sent by Him into every nation to publish these things 2. that rather among the Gentiles [than among the Jews] men should believe in Him 3. predicted 5000 years before He appeared 4. predicted 3000 years before He appeared 5. predicted 2000 years before He appeared 6. predicted 1000 years before He appeared 7. predicted 800 years before He appeared If we don't know to which prophecies he refers, then how do we know he wasn't mistaken?