the bond order of CN^- is

Valence electrons in CN^- = 14 electronic configuration K K ^* ${\left(\sigma 2s\right)}^2{\left(\sigma *2s\right)}^2{\left(\pi 2p_x\right)}^2{\left(\pi 2p_y\right)}^2{\left(\sigma 2p_z\right)}^2$

Bond order $=\frac{\mathrm{Bond}\text{ electrons -antibonding electrons}}{2}=\frac{10-4}{2}=3$