You can migrate from WordPress releases 5.0.x and 4.9.x to a calmPress 0.9.x release following the general migration from WordPress guide.
If you are using an earlier WordPress version, the migration might work but it would be better to first upgrade your WordPress to at least 4.9.8.
At the time of writing the WordFence plugin have an option which is on by default which might produce false positive when it tries to detect if core files had change. Obviously once the migration is finished you are not on WordPress any longer and the test at best do not tell you anything you do not already know.
While other parts of WordFence functionality will continue to work and be useful, we do not find that specific option to be useful in any case as if you have a bad code on your install it will most likely be able to hide its existence by interacting with the WordFence functionality, therefor it is fully safe to turn the “Scan core files against repository versions for changes” (located at the “scan” options section) option off.