Maximize the size of child form in parent form of MDI

Private Sub PendaftaranAhliToolStripMenuItem1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PendaftaranAhliToolStripMenuItem1.Click

        Form3.MdiParent = Me

        Form4.Close()
        Form5.Close()
        Form6.Close()
        Form7.Close()
        Form8.Close()

        Form3.Show()
    End Sub