[Stiebler]

Copy all the optional mods in the documentation folder of NYGM versions into a folder called silenthunteriii\mods (I assume that your original SH3 folder is found in silenthunteriii\data).

Copy these optional mods in the order of their versions.
That is, start by copying the mods from NYGM 2.5, then from NYGM 3.2, then from NYGM 3.3B, then from NYGM3.3C.

You will discover that some of the later optional mods replace earlier versions. That is deliberate, always copy the latest version last.

Finally, use J Scones' ever-popular, always valuable, JSGME to install selected optional mods from silenthunteriii\mods into your games folder silenthunteriii\data.
Then later you can remove any optional mods easily, if you do not like them. Some are intended only for use at different times of the war; for example the FuMB37XXIII mod should never be installed before October 1944.
All the optional mods have their own (short) documentation, so read these documents first.

Stiebler.