Export 22,000 Gmail threads to CSV

I am looking for a developer to help me to export 22,000 gmail threads into a CSV file with conversations in a single description field in html format. The data needs to be restricted to 30,000 records. The CSV headers will need to satisfy a template provided by my CRM tool, Freshdesk, for subsequent upload as tickets into the system. See Freshdesk required template attached . The sheets labelled tickets and notes conversations are the most relevant to this project - yellow fields are mandatory.