Migrating widnows 6.5 Application to Windows 8.1 embedded

Good day;

We have a number of applications that were developed using Windows mobile 6.5 for Motorola ES 400 devices and other legacy type devices for our manufacturing and maintenance teams. Now we wish to move to a more modern device running Windows 8.1 embeded, whether these rugged devices come from Blue Bird, Motorola, or Honeywell is not important at this time. What is important to our team is the ability to refactor our code from 6.5 to 8.1 or is this going to be a 100% re-write?

Has anyone found and 3rd party tools to assist in this?

Can anyone share their experience in this area?

Anything you can share would be most welcome.

Thank You
ThaiFishing