It hasnt been released on the PS1. It's going to be out for the DS, and you can only get the Japanese version for the Famicom (NES in Japan). It was never released in America.

Unless you're talking about Final Fantasy VI, which was first released in America under the name Final Fantasy III. In that case, it's available for the SNES as FFIII, and for the PS1 as part of Final Fantasy Anthologies (unless you're in Europe, in which case I believe it was released simply as Final Fantasy VI. Check the FAQ in the FF 1 - IV forum for more info.