Hmm, I don't know enough to give you a confident answer yet. However, there is an open contribution adding the option of multiple accounts, but it is currently blocked: [GitHub PR #8237](
https://github.com/airbytehq/airbyte/pull/8237). For now, you might need to set up multiple Facebook Marketing connectors for each account. You can follow the setup guide for Airbyte Cloud in the [Facebook Marketing source documentation](
https://docs.airbyte.com/integrations/sources/facebook-marketing). If you have any further questions or need assistance, feel free to ask!