How to find a specific window?

Hello, I'm trying to find a specific window and put it on top, but I'm stuck, I don't know how to do this. This is my code:

vb.net Code:

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
    Private Declare Auto Function SetActiveWindow Lib "user32" (ByVal hwnd As IntPtr) As Integer
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim hwnd As IntPtr = FindWindow("MozillaUIWindowsClass", vbNullString)
        SetActiveWindow(hwnd)
    End Sub

Thanks a lot..!