When we do dimensional analysis, we do something analogous to stoichiometry, but with multiplying instead of adding. Consider the diffusion constant that appears in Fick's first law: J= -Ddn/dx

In this expression, J represents a flow of particles: number of particles per unit area per second, n represents a concentration of particles: number of particles per unit volume; and x represents a distance. We can assume that they have the following dimensionalities:

[J] = 1/L2T
[n] = 1/L3
[x] = L

Required:
From this, determine the dimensionality of D.