For importing movies: two ways, depending on the state of your existing media.
Point Radarr to your media. It might detect everything. Radarr will let you set rules for file name and structure. Follow jellyfin guidelines. Then let Radarr reorganize your files to the new structure. Then import to Jellyfin
If it’s very disorganized, you might have to organize it according to the jellyfin guides yourself, or script it if you can, before importing to jellyfin.