You can use the ProForma Export API to extract data from ProForma forms. The API allows you to filter for the desired Jira issues, select which ProForma fields to include in the export, select additional Jira fields to include. Data can be exported in a JSON or XLXS format.
Please see our developer site for detailed instructions for using the API.
Currently, ProForma APIs are only available for Server and Data Center. We will continue to work with Atlassian to extend this feature to Cloud customers.