We know that the electrostatic force = Kq1q2/r2
And the electric field= kq1/r2
We can also say that field=force/charge
Now force = mass * accn
Accn = metre / time2
Dimensions of force = M1L1T-2
Charge = I(current), * time
The dimensions of the charge = A1T1
This is how the field dimensions are = M1L1T/A1T1 =
= M1L1T^-3 A^-1
We are grateful for his help. !