Go to Leviticus 25:8-12. This is a bit about the year of Jubilee. We will see that the blowing of the trumpets had another idea behind it, not just the announcing the plagues of God's judgment on Jericho, and the people, but it was also announcing the jubilee.
Here, we are getting into a bunch of sevens again.
It says that the Jubilee is a holy year of liberty, and that is exactly what God was doing here in destroying Jericho. He was proclaiming liberty, not for the people of Jericho, but for His own people. He was going to make them free to inherit the land. That is one big part of the jubilee year - everyone goes back to his inheritance. No matter what had happened in the intervening time, you get back what is yours by right, or reward in this case.
That is the same thing that happens in the Millennium. The inheritance goes to those to whom it has been given - the people of God.
The same thing is happening by the fall of Jericho as will happen in the Millennium. The Jubilee is a type of the Millennium, which is begun by the fulfillment of the day of Trumpets.
We saw in Revelation 11 that the last trumpet announces the coming of Christ. This is also in Matthew 24:30-31 and I Thessalonians 4:16.