How to convert polydata vtk file to structured grid vtk file

I want to get a structured or unstructured (but not using triangulation, and preserving the original grid) version of that VTK file written as “POLYDATA DATASET”.
To make things simple, I will try to give a very minimal example:

Suppose that I have grid: my_domain.vtk that looks like:
mesh_domain
But this file my_domain.vtk contains: the following at the header:

....
....
DATASET POLYDATA
...

My question is how to convert this file to a structured grid (or at least unstructured if tha makes sense but keeping the grid intact) not a polydata.

Most of the tools I use expect the VTK file to be either in STRUCTURED_GRD or UNSTRUCTURED_GRD but not POLYDATA.

Thanks