First of all, the present population of the world is now around 7 billion people. The prophecied 70th week [7 years] of Daniel 9:27, the 7 year tribulation, will soon take place. When it is over, it will kill two thirds of the 7 billion people on earth, to approximately 2.33 billion, according to Zech.13:8. Jesus will establish His 1,000 year kingdom on earth, according to Rev.20:6, after throwing Satan into the Abyss for 1,000 years, in Rev.20:1-3, and the 2.33 billion will all be Jesus subjects.
Notice, in the first resurrection, all the participants will be made priests of God and of Christ, in Rev.20:4 and 6. None of the 2.33 billion people will be saved when the 7 year tribulation begins, or they would have been raptured with the Church before the 7 year tribulation begins, according to Jn.14:2-4, 26; 1 Thess.4:16-17 and 2 Thess.2:1-8.
God will place 144,000 converted Israelite evangelists on the earth from heaven, in Rev.7:1-8, as He will also do with His two witnesses of Rev.11:3. They will bring millions to the Lord in the absence of the departed Church as recorded in Rev.7:9-17. Most of whom paid for their salvation with their lives according to Rev.20:4.
However, when the 1,000 years in the reign of Christ here on earth, Satan will be released. He will rebel against God and establish a huge army of all the people of the earth, who never came to belief in Jesus during the tribulation.
Satan will bring them up against God's people surrounding Jerusalem, and God will destroy Satan's armie and throw Satan into the lake of fire, where he will remain forever, in Rev.20:7-10.