There are many ways of doing this. My favorite is to loop through the list box and taking each items text and adding that to the text box. I hope this helps?
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
For Each item As String In ListBox1.Items
TextBox1.Text += item.ToString & vbCrLf
Next
For Each item2 As String In ListBox2.Items
TextBox1.Text += item2.ToString & vbCrLf
Next
End Sub