Models must be placed in the directory 'model' which is normally Program Files\FMS\model.
Opening a 'zip' compressed file, you will get several files like .par,.wav, .x,... with the plane name as first part. These files must be in the 'model' directory [i]or can be organised in a subdirectory (bearing the model name ?) under the 'model( directory, to obtain a better organized storage.

You probably got your files downloaded at another place. Try to find them, and move them at the right place.

Phil.