You can't add threads directly to a listview - ProcessThread does n't override ToString, so all you would get is
System.Diagnostics.ProcessThread
for each one.
And you can't do it that way anyway!
For Each p As Process In Process.GetProcessesByName(Form1.TextBox1.Text)
Console.WriteLine(p)
For Each pt As ProcessThread In p.Threads
Console.WriteLine(" {0}", pt)
Next
Next
Will at least give you some code that works as a starter!