Why isn't this configuration saving?

Question

How do I do change configuration when there is a dash in the yml file?

The configuration is the following one.

source:
  plugin: url
  data_fetcher_plugin: http
  data_parser_plugin: xml
  urls:
    - 'private://migrations/migration.xml'

I need to change it to the following.

source:
  plugin: url
  data_fetcher_plugin: http
  data_parser_plugin: xml
  urls:
    - 'private://migrations/2023-05-01/migration.xml'

I tried the following code, but it does not work.

$this->configFactory()
  ->getEditable('migrate_plus.migration.my_migration')
  ->set('source.urls', $file_values->uri);

$this->configFactory()
  ->getEditable('migrate_plus.migration.my_migration')
  ->set('source.urls', [$file_values->uri]);