I don't want a link to a mod or something, because I guess it is not allowed to share stuff from one game to another.

I just want to ask if it is possible to get some weapons and armours from my New Vegas game and convert them to my Fallout 3 game?

I want to convert some of the Combat Ranger suits to Fallout 3 for my personal use.

Yes it is.

But it is against the rules to dicuss how to do it.

The use or transfer of assets from one game to another is not permitted.