from what I understand, it can't be done, there is no exporter, the Aftermath people have somehow managed to use some sort of expensive Model capturing software to capture the meshes for their project, but they won't tell anyone what they used. However, many of the Legacy meshes were designed by Rick Knox (AKA Pneumonic81/P81/Knox1701), who used to mod Bridge Commander and SFC, and he imported many of his BC/SFC meshes into Legacy, so, chances are you can probably find what you need by looking up his old mods on BCFiles or SFCFiles.