First, there must be the rapture of the church. The Bible does not tell us when this happens. It tells us no one knows except God the Father (Matthew 24:36).
The rapture will happen BEFORE the Mark of the Beast. In the rapture, Jesus will take all believers, living and dead, from the earth (1 Thessalonians 4:13–18; 1 Corinthians 15:50–54).

Then shortly after the Antichrist will sign a covenant with many nations concerning the city of Jerusalem (Daniel 9:27). This signing ceremony is the beginning of the seven-year tribulation period. The Seventy Week Prophecy of Daniel (70 sets x 70 years) that marks the time of God’s interaction with Israel. Sixty-nine of those weeks have passed since Daniel’s writing. The final week will be what we call the tribulation, which is when the Antichrist, or the beast, will rise to power. This Beast will join together ten nations (Daniel 7:24–25; Revelation 17:7) and make a deceptive treaty with Israel (Daniel 9). The mark of the beast CAN NOT exist without the beast/Antichrist demanding it. The mark of the beast CAN NOT exist until the beast himself is in power during the tribulation.

Halfway through the tribulation period, the mark of the beast appears. It will be introduced by the False Prophet. (Revelation 13:16).
The mark of the beast does NOT exist yet. Many want you to believe the covid vaccines are the Mark of the Beast. This is incorrect and does not line up with what was prophesied in the King James Bible.

The seven-year Tribulation ends with the return of Jesus Christ at the Battle of Armageddon (Revelation 19:11-21). At this point, Jesus establishes His 1,000-year reign over the earth (Revelation 20:1-4).