That should be Metasequoia LE. Light Edition. The free version.
To use a file in FMS you'll need to save your model file as a .x file from within Metasequoia so the file would be "modelname.x" where "modelname" is the name of your model. You'll also need a "modelname.wav" file for the motor sound, a "modelname_prv.jpg" used by FMS for previewing the model when you "Load" the "Model" within FMS and a "modelname.par" file version beta7 or version alpha8 that describes the flying characteristics of your model. The .par file can usually be copied from another model that flies like yours and renamed to your models name.
Other files you may also have include modelname.bmp which would be a 256x256 or 512x512 .bmp file used to apply textures to your model within Metasequoia LE, a modelname-readme.txt file describing the model and contact information for the modeler.
Usually you'll find all these related files within a "modelname.zip" file that's downloadable from the web.
Some additional details are available at .
-- ggunners

