Organization structure chart

If by organization structure chart you mean a drawing representing authority relationship in an organization, you must be aware that ISO 9001:2015 has no requirement for the existence of an organization chart. Also, ISO 9001:2015 has no mandatory requirements for procedures. ISO 9001:2015 has no mandatory procedures. Please check this article - List of mandatory documents required by ISO 9001:2015 - https://advisera.com/9001academy/knowledgebase/list-of-mandatory-documents-required-by-iso-90012015/

Auditing an organization requires checking evidences from reality against audit criteria. As audit criteria you will have ISO 9001:2015 requirements and any internal rules and procedures, written or not written according to clause 4.4.2.

You can start your audit preparation by asking the organization its mandatory documents and a list of internal rules or procedures. If the organization has nothing, perhaps it is best to perform a Gap Analysis instead of an internal audit.

You can find more information below:

• Gap analysis vs. internal audit in ISO 9001 - https://advisera.com/9001academy/blog/2015/02/17/gap-analysis-vs-internal-audit-iso-9001//
• Free Gap Analysis Tool - https://advisera.com/9001academy/iso-9001-gap-analysis-tool/
• ISO 9001 Audit Checklist - https://advisera.com/9001academy/knowledgebase/iso-9001-audit-checklist/
• How to create a checklist for an ISO 9001 internal audit for your QMS - https://advisera.com/9001academy/blog/2016/07/12/how-to-create-a-check-list-for-an-iso-9001-internal-audit-for-your-qms/ 
• Free webinar on demand - How to perform an ISO 9001:2015 internal audit - https://advisera.com/9001academy/webinar/how-to-perform-an-iso-9001-2015-internal-audit-free-webinar-on-demand/
• ISO 9001:2015 Lead Auditor Training Course - https://advisera.com/training/iso-9001-lead-auditor-course/
• ISO Internal Audit: A Plain English Guide - https://advisera.com/books/iso-internal-audit-plain-english-guide/