With any mod, is best to apply aka activate them, through the use of jsgme.
It also pays to make sure that the mod structure... even if it is, "just 1 mod" as you're signifying here... is that typhoon mod... is correctly set up. Meaning that it isn't double nested... for example :
mod name\mod name then the subsequent folders & files of the mod, for it to work with your copy of SH4.
Also of import, is that the mod you're attempting to use, will work for the exact version of SH you have... in this case, SH4. Note... that there are at bare minimum, that I'm aware of that are still out there, in the wilds... aka availability... Silent Hunter IV wolves of the Pacific (v1.4) & Silent Hunter IV wolves of the Pacific: Uboat Missions (v1.5) I know that Steam, has both versions on their store front for getting acces to... & Ubi, last I know of.. has just 1 verion copy available to get from their store... & that, is hot listed there, a... "Gold" edition.
Getting it from other sources... is no guarantees, of getting the right version... as some may have access to the very early on releases of SH4... that would end up with your having to find the patches for them, to be=ring them up to v1.4 status, at least & or v15, at best... and even then... could well run into issues with the patches.
Best advice... avoid any possible issues with all of that & just simply grab a copy from either Steam, or Ubi... & make sure to NOT install it in either of Window's "Progam file" locations.... EVER.
Armed with that info that KM gave you... & the base info I added to that... you should then have no issues with getting the mod in question to work.
M. M.