In the given complex [E(en)2(C2O4)]NO2 ethylenediamine is a bidentate ligand and (C2O42−) oxalate ion is also bidentate ligand. Therefore, coordination number of the complex is 6 i.e., it is an octahedral complex.
Oxidation number of E in the given complex is x+2×0+1×(−2)=+1⇒x=+3