NHM Converter : Online  

Your Tamil content may be in many different font encodings. You can
convert one encoding to another, instantaneously, amongst the following
encodings: Unicode Tamil, TSCII, TAM, TAB, Diacritic, Bamini,
Shreelipi, Vanavil and Softview. If you come across any new encoding,
just inform us and we will make that work too!

You can use this service here.