Find the total number of moles of donor atoms present in one mole $\mathrm{K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right]$ complex.

The complex $\mathrm{K}_4[\mathrm{Fe}(\mathrm{CN})_6]$ contains the coordination ion $[\mathrm{Fe}(\mathrm{CN})_6]^{4-}$ with iron as the central metal atom coordinated by six cyanide ligands.

Cyanide is monodentate with carbon serving as the donor atom, contributing one donor site per ligand.

Since there are six ligands, each providing one donor atom, one mole of the complex contains exactly six moles of donor atoms.

$\boxed{6}$