Coordination number of cobalt in [Co(en)2Br2]cl2???

The coordination number of ##Co## in ##[Co(en)_2Br_2]^(+)## is 6.

Ethylenediamine is a bidentate ligand; it has 2 donor atoms to coordinate to the metal centre in a 5-membered chelate ring. Note that this (I presume) is a ##Co^(3+)## complex, i.e. ##d^6## configuration, whose formula is ##[Co(en)_2Br_2]^(+)##, not as quoted in your question.