Hello!
We can use the following equation:
[tex]V = Ed[/tex]
V = Potential Difference (V)
E = Electric Field (N/C)
d = distance between plates (m)
Begin by converting 4.1 mm to m.
1 mm = 0.001 m
4.1 mm = 0.0041 m
Now, we can solve for the electric field strength.
[tex]E = \frac{V}{d} = \frac{8.5}{0.0041} = \boxed{2037.17 \frac{N}{C}}[/tex]