just go to the minecraft forge website, look for forge 10.13.3.1391 (as of me typing this now) download installer, go to server set to folder, run it without mods on your pc, let the files generate, copy all mods except nei,tinker tooltips, ect to the mods folder, copy your world, and configs to configs folder. Run the server and have fun. (havent actually done this yet, but that is how i make my instances. its pretty straightforward) SOME PACKS ARE DIFFERENT THAN OTHERS SOME REQUIRE STUFF LIKE CUSTOMNPCS FOLDER AND SIMILAR