Total number of lone pair of electrons in I 3 - ion is:

The structure of ${{\mathrm{I}}_3}^{-}$ ion is:

As we can see central atom has 3 lone pair and two bond pair and outer atoms has 3 lone pair each. So, there are total of 9 lone pair. Central atom will have ${\mathrm{sp}}^3\mathrm{d}$ hybridisation and linear shape.