https://understanddrupal.com/articles/migrating-csv-files-drupal

image_migration_process.yml

process:
  psf_destination_filename:
    plugin: callback
    callable: basename
    source: photo_url

image_migration_source.yml

source:
  plugin: csv
  path: modules/custom/ud_migrations/ud_migrations_csv_source/sources/udm_photos.csv
  ids: [photo_id]
  header_offset: null
  fields:
    - name: photo_id
      label: 'Photo ID'
    - name: photo_url
      label: 'Photo URL'

node_migration_process_destination_and_dependencies.yml

process:
  field_ud_image/target_id:
    plugin: migration_lookup
    migration: udm_csv_source_image
    source: photo_file
destination:
  plugin: 'entity:node'
  default_bundle: ud_paragraphs
migration_dependencies:
  required:
    - udm_csv_source_image
    - udm_csv_source_paragraph
  optional: []

node_migration_source.yml

source:
  plugin: csv
  path: modules/custom/ud_migrations/ud_migrations_csv_source/sources/udm_people.csv
  ids: [unique_id]

paragraph_migration_process.yml

process:
  field_ud_book_paragraph_title: book_title
  field_ud_book_paragraph_author: 'Book author'

paragraph_migration_source.yml

source:
  plugin: csv
  path: modules/custom/ud_migrations/ud_migrations_csv_source/sources/udm_book_paragraph.csv
  ids: [book_id]
  header_offset: null
  fields:
    - name: book_id
    - name: book_title
    - name: 'Book author'

udm_book_paragraph.csv

udm_people.csv

udm_photos.csv