Impossible to know anything. You have not offered any system information, no version info for AI, no details about when this error comes up, no specifics about the document or tools you may use and so on.
adobe Illustrator , the message pop up when i go to export
Sorry to hear about this. I hope your issue is resolved by now.
If not, please follow suggestions given on this community post(https://community.adobe.com/t5/illustrator/quot-the-operation-cannot-complete-because-of-an-unknown-...) & let us know if it helps.