Welcome to the Make community!
The “Create a Completion” module does not support file uploads.
Try using the OpenAI “Message an Assistant” module:
Send messages to a specified or newly created thread and execute it seamlessly. This action can send the arguments for your function calls to the specified URLs (POST HTTP method only). Works with Assistants v2.
For more information, see https://www.make.com/en/integrations/openai-gpt-3, and https://www.make.com/en/help/app/openai-gpt-3 in the help centre.
Related threads:
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Investing some effort into the Make Academy will save you lots of time and frustration using Make.