This is a dilution question where it can be solved as follows.

The number of mole of the disinfectant in a #V# volume of the stock solution (we will call it) #n_s# is equal to the number of mole of the disinfectant in 2.00 L of the hand-soap solution (we will call it) #n_h#.

This would give us: #n_s = n_h#

In general, the number of mole #n# is related to the concentration by #n = C xx V# where #C# is the concentration and #V# is the volume.

Therefore, #C_s xx V_s = C_h xx V_h#

#C_h = 0.400 "mol/L" and V_h = 2.00L#

To calculate the volume of the disinfectant #V_s = (C_h xx V_h)/C_s# you will need the value of #C_s# which is the concentration of the disinfectant stock solution.