Hello From the site "The Sims resource " it is possible to download over 56.000 3D human characters. A small fee must be paid and there is no any any copyright information both in the site and in the attached .txt file ( at least I did not find it ) Is it "inplicit" that I am allowed to use the models with "The Sims game "only but it is forbidden a commercial game use ? thanks in advance

link please, to both the main site and where it says what you're describing.
thanks.

When in doubt, don't. I wouldn't use the models in any commercial projects.

If you need 3D models, look at turbosquid.com. They have both free and pay models for use, and you can use them in any project.

http://thesimsresource.com/

As far as I see there is not any restriction for the use of the dowloaded models, ( they are not free even if the cost is very low) but I was told that in such a case copyrights are inplicit ,unless the models are declared as public domain

Copyright is always explicit. When something is created it is protected by copyright regardless of if the owner puts a notice or not. Use is always restricted unless they state otherwise.

To use the files commercially you would need permission from the author/creator/owners of the files. However one question arrises - why would you want to use files that are clearly from another game in your game? People will almost certainly recognise them and think your game is a bit lame as it doesn't have its own art.