First off, don't use the letter 'N' as a word in your questions. It's hard to answer questions when they are in code. I'm assuming you mean "and" and not "in"?
Did you read the "Readme" file that should have been included in the Zip file with the Mod you downloaded?
Most "Readme" files have installation instructions. Unfortunately, some do not. I guess the authors figure everybody should know this stuff. Of course some people are doing this for the first time, so every "Readme" file should have that information.
I can't think of ANY reason why would put anything in the ProMod directory. ProMod version3 already comes with a jetpack.
Most MODs need to be in the 'BASE' directory. Also, in case you didn't know, the PK3 file is the MOD. Don't put the Zip file you downloaded into the base directory. You need to Unzip the Zip file and THEN put the PK3 file in the base directory. Maybe you already knew that, but like I said, this is new stuff for some people.
Hope that helps.