This can be translated as "coming down in a cloud."
## with power and great glory ##
This can be translated as "powerfully and gloriously" or "and he will be powerful and very glorious." "Power" here probably refers to his authority to judge the world. "Glory" here may refer to a bright light. God sometimes shows his greatness with a very bright light.
## stand up ##
This can be translated as "stand up with confidence." Sometimes when people are afraid, they crouch down in order to avoid being seen or hurt. When they are no longer afraid, they get up.
This is an idiom meaning "look up." By looking up, they would be able to see their rescuer coming to them. (See: [[rc://en/ta/man/translate/figs-idiom]])