Here, 

We know pressure is defined as the perpendicular force applied for unit area. So,

Pressure(P) = $ \frac{Force(F)}{Area(A)} $

or, P= $ \frac{Newton(N)}{m^2} $

or, P= $\frac{kg}{m.s.s} $

Hence, The fundamental units involved in the unit of pressure are Kilogram(kg), Metre(m) and second(s).