Hey Minh, 

Thanks for reaching out! If you purchased or duplicated the file / design from the Figma Community, you might be able to reach out to the creator directly through the original Community page. Sometimes creators leave contact info or links there.

For example a UI Kit file in the Figma Community:

Still, if the profile and file are no longer available, the creator may have removed their content or deactivated their account, so their details might no longer be accessible. Hope this clarifies!