Hi Ricardo,
Thank you for reaching out. You can follow this guide for uploading offline conversion. You will use the ConversionUploadservice and need to provide the required information (gclid, conversionName, conversionTime). Please refer to this code example. Let me know if this is what you're looking for. If not, can you please elaborate your concern and provide screenshot of the UI so that I can further investigate the issue.
Thanks,
Nirmita Patel Google Ads Team