Your company has an existing GCP organization with hundreds of projects and a billing account.

Link the acquired company’s projects to your company's billing account.

Configure the acquired company's billing account and your company's billing account to export the billing data into the same BigQuery dataset.

Migrate the acquired company’s projects into your company’s GCP organization. Link the migrated projects to your company's billing account.

Create a new GCP organization and a new billing account. Migrate the acquired company's projects and your company's projects into the new GCP organization and link the projects to the new billing account.