where can i get a parts number fmtc190ms for my circular saw?

You seek a part number but do not say what part you need.

The machine is a Performance Power (B&Q) Mitre Saw with a 190 mm blade.

Any blade supplier will sell you a 190 mm blade if that's what you want but Solent Tools specialise in Performance Power spares.

023 8057 8057

It may be that fmtc190ms is actually the part number you want - I decode it as follows
(f) Mitre - tungsten carbide - 190 mm mild steel

Good Luck...
December 2015