If I understand correctly, it is recommended to use original MRI files as an input. However, I have only *.mri file. First, I was able to run reconstruction following fieldtrip pipeline which includes some preprocessing of *.mri and writing resulting files in *.mgz format that can be used by Freesurfer.  Is there any other way to work with *.mri files in Freesurfer without these preprocessing steps?

Many thanks!