Broken circular saw ?

Hi, As a mere woman, I have a wonderful circular saw which I have used all winter to supply logs for my wood burner. However, repairs are not my strong point. My problem is the engine whirrs and the handle comes down but the blade will not turn. I have a FMTC 190 ms . What is the problem ? I think it might be the belt has gone, but any advice please and also where do I get a new belt if that is the case. Thanks Lin