Jeremiah often uses these words to introduce an important message from Yahweh. See how you translated this in Jeremiah 6:6.
“Daughter of Babylon” here is another name for the people who live in Babylon. (See: rc://en/ta/man/translate/figs-metonymy)
People thresh grain by trampling it on a threshing floor, and Yahweh speaks of people punishing the daughter of Babylon as if they were threshing grain. (See: rc://en/ta/man/translate/figs-simile)
Yahweh punishing the daughter of Babylon is spoken of as if he were trampling and threshing grain on a threshing floor. AT: “It is time to punish her” (See: rc://en/ta/man/translate/figs-metaphor)
The harvest is a metaphor for the result of the actions that the people did before. Babylon will experience the result of its people’s sins. AT: “God will punish her for her sins” (See: rc://en/ta/man/translate/figs-metaphor)