You need to send an email to that marketplace, find their contact. Here is a template I found, it should do the trick
Dear Designated Agent:
My name is [Your name].
Your website or a website that your company hosts is infringing on a copyright-protected 3D model owned by myself. The original 3D model, entitled “[Title]”, to which I own the exclusive copyrights, is located at: [URL where you originally published the model]
The unauthorized and infringing copy is located at: [The website using your work without permission]
This letter is official notification under Section 512(c) of the Digital Millennium Copyright Act (”DMCA”). I seek the removal of the infringing material referenced above.Please take note as a service provider, the Digital Millennium Copyright Act requires you, to remove or disable access to the infringing materials upon receipt of this notice.
The Online Copyright Infringement Liability Limitation Act grants service providers such as your company immunity from liability so long as investigate and rectify this copyright violation in a timely manner. Should your company fail to do so, it may become liable for the infringement.
Please remove and disable all access to the aforementioned copyrighted work immediately. I have a good faith belief that use of the copyrighted materials described above as allegedly infringing is not authorized by the copyright owner, its agent, or the law.
I swear, under penalty of perjury, that the information in the notification is accurate and that I am the copyright owner or am authorized to act on behalf of the owner of an exclusive right that is allegedly infringed.
Best regards,
/s/[Your name]