Hybridization, shape, and magnetic moment of ${\mathrm{K}}_3\left[\mathrm{Co}{\left({\mathrm{CO}}_3\right)}_3\right]$ are:

K₃​[Co(CO₃​)_3​]
     +3              d⁶ configuration
weak ligand so no pairing and high spin complex forms
so sp³d² hybridization takes place and octahedral complex forms
Also as it have 4 unpaired electron so 
magnetic moment
μ=n(n+2)​=4.9 BM
n = no of unpaired electron