Resistance between parallel wires in an insulator?

Hi all,

New here...I was wondering if anyone knows a formula to calculate the (insulation) resistance between two parallel conductors buried in an insulator. For example say 2 copper pins of 1mm diameter spaced 2mm apart over a 20mm length in a plastic (ptfe). The numbers/material are not specific to what I want to do just for example purposes.

Any help would be great as I've seen stuff for concentric cylinders but nothing for parallel conductors.