Modern revelation makes it clear that the saints will remain on the earth through the tribulation period until Christ's coming and those who are old or in the grave shall be changed to a resurrected state at that time. Younger saints will grow old and be changed in an instant at one hundred years of age (Isaiah 65:20; DC 101:30-31) to inherit a glorious resurrection with God and Christ.
Question: Do Mormons believe in the "rapture"? - FAIR (fairlatterdaysaints.org)
Modern revelation makes it clear that the saints will remain on the earth through the tribulation period until Christ’s coming and those who are old or in the grave shall be changed to a resurrected state at that time. Younger saints will grow old and be changed in an instant at one hundred years of age (Isaiah 65:20; DC 101:30-31) to inherit a glorious resurrection with God and Christ.
Not sure where that quote came from, although it isn’t in quotation marks. If you were to refer to the tenth Article of Faith you might find a more relative quote. Ultimately the Earth will be a celestial orb, but before that can happen where no unclean thing can dwell much less tolerate it must return to it’s original state when Adam and Eve were living in the Garden a state that man also needs to pass through in preparation for the celestial.
The three states are telestial, the one we now experience, Terrestrial, the one that existed for Adam and Eve before being removed from the Garden, and the final state Celestial. In the tenth Article of Faith it is referred to as paradisiacal glory. Your quote indicates happenings out of sequence. Man will still be subject to death both physical and spiritual during Christ’s thousand year reign on earth and I don’t believe the instant resurrection at his coming except for those already dead worthy of resurrection, and worthy of coming in the clouds with Him.
His coming is the beginning of the thousand years, life goes on.