The teaching in this passage is that Christ has become the first fruits of the dead—He was the first to be resurrected from the dead; and then all true believers in Christ will correspondingly be made alive in their own order. This means that there will be a certain order of resurrections of all believers of all times.
The first resurrection will be of church believers just before those who are raptured (1 Thess. 4:15-17). The next two resurrections will be of the tribulation saints and the Old Testament saints. These resurrections will be at His second coming, just before the millennial kingdom. The last resurrection will be of the believers during the millennium. We don’t know exactly when this will occur. They may be resurrected to eternal life individually, immediately after each one dies; or they may possibly be resurrected all at once just prior to the destruction of the heaven and earth (Rev. 21:1). (The last three groups are not in Christ in the sense that they are of the church; however, they are in Christ in the sense that Christ’s blood has saved them.)
So when Paul states that each one will be made alive “in his own order” at His coming, “His coming” here is not one specific event, but I believe it refers to the entire time period between the rapture and the second coming; and then it even extents past that, to include the millennial believers. And we know that it extends that far because of verse 24, which speaks of the eternal kingdom—the new heaven and earth.
With all that said, the whole human race, from all times, may rejoice—if they are believers; for Christ blood has reached them all. And because He died for them all, and was raised, they too—all of them—will be raised to see Him and to enjoy His glory forever!