If you only want to migrate files you will have to copy the contents of the upload folder and the contents of the project_files and project_file_revisions. Plus you will have to somehow "connect" the database data that you migrate (e.g. the created_by_id column of project_files should correspond to an id in the users table, etc.). You will also need to migrate the entries of the workspace_objects table that correspond to files (the ones that have 'ProjectFiles' in the 'object_manager' column) and the same with object_subscriptions, application_logs, comments, tags, custom_properties, linked_objects, object_properties, read_objects, searchable_objects. If you already have files in the target database you will have collisions. You will have to change some IDs before inserting the rows. If you are using database storage you also have to migrate tables file_repo and file_repo_attributes.
