Note that those quotes aren't '"', they are text processor "special quotes": '“' at the beginning, and '”' at the end.
Try this:
Dim s As String = myTextBox.Text
s = s.Replace("1", "Q1")
s = s.Replace("2", "Q2")
s = s.Replace("""", "")
s = s.Replace(""", "")
s = s.Replace(""", "")
myTextBox.Text = s