what should be the reverse voltage of diode
You need at least the peak voltage. That is 230V + 10% * SQRT(2) ~ 360 Vpeak.
(Mains voltage isn't solid 230V, it has margin)

However, you also need to survive transients (IEC 61000-4-4). Which is why you use slightly higher Vr. Diodes of 600V to 800V are common and 1000V to 1200V are becoming affordable as well.

Make sure to protect the input with an appropriate varistor (MOV) and fuse.