What does Jeremiah mean in Chapter 4 when he says "there were NO MEN and ALL the cities were broken down"? Is he speaking about Noah's flood?
Chapter 4 of Jeremiah is not set in the time of Noah nor in any other time of Genesis. Jeremiah 4 is speaking of the events of the seven-year Tribulation that will come upon Israel immediately before the Second Coming of Christ. We are still waiting for the fulfillment of this prophecy.
In his previous chapter, Jeremiah explained the terms for Christ’s return and the arrival of the kingdom for Israel. Israel would see this glory only if and when the nation repented, confessing their sin for rejecting the Messiah and accepting Jesus as their Messiah:
As Israel receives the Lord (see v.19) the Lord will bring the blessings of the kingdom to Israel. Notice the promises in this passage are clearly speaking of an obedient and repentant Israel receiving the Kingdom in a future day. These are not matters of the past but of the future.
Then in chapter 4, the Lord continues this discussion by moving to describing the consequences for Israel failing to repent. The consequences described in chapter 4 are the plagues, judgments, and disasters of Tribulation, which are described in various places in the OT and in Revelation.
For example, in 4:20-26 the Lord describes the outpouring of His wrath upon the Earth and the utter devastation that it produces: cities with no inhabitants, mountains brought low, celestial bodies cease giving their light and human population virtually extinct. These consequences mirror the descriptions of Tribulation found in Revelation 6-18.
When Jeremiah says the earth is “formless and void,” he’s invoking the description of Genesis 1 to emphasize the complete chaos and destruction that is coming upon the earth because of Israel’s sin. He’s not describing a literal repeating of the Genesis 1 moment or circumstances, but rather he’s associating the one with the other to emphasize the magnitude of the destruction in Tribulation.
Tribulation is a period of judgment brought upon the whole earth but aimed specifically at Israel. In fact, later Jeremiah calls the time of Tribulation a time of "Jacob’s distress:"
Notice the similarity of the language describing this coming time of great destruction.
For a more detailed accounting of these matters, we highly recommend you listen to our Revelation Bible Study available online for free. This study covers the purpose and events of Tribulation as they relate to Israel.