i put it into the conquests\scenario map but nothing changed
You moved the whole mod across, i.e. the mod-folder plus the .biq? If so, you
should now be able to see the .biq in the 'Civ-Content' menu.
If you can't, then do you have Admin privileges and/or is the game running as Admin? Admittedly I don't have the Steam version of C3C, but AFAIK, the .
..\SteamApps\ directory — including the Civ III subdirectory — is usually added to the
protected C:\ProgramFiles(x86)\ directory by default. Without Admin, it's therefore
possible that the mod may actually have been Virtual-Stored on your machine, rather than being added to the 'real' game directory: if that's the case, the game .exe still might not be able to 'see' the mod.
If the above still doesn't help, you could try reposting this question in (or asking a Moderator to move this thread to) the "Creation & Customisation" subforum.
Including a screenshot of your current Civ III directory structure(s) would probably be useful as well.