IronPython in Unity 5.5.0

Hi everyone,

for my internship, I need to extract a method from a python script and receive the int return of this method in a C# script.
So I looked on the web and I saw that IronPython was able to do so.
The fact is, I need to import 4 dlls to make it work. I put them in an Assets/Plugins folder in my project and the .meta files appears.
But I can't use them because when I write "using IronPython;" , visual studio just tell me that the name IronPython can't be find..

So if someone have an explanation for me, I would be very grateful.

PS : I can't change my Unity version, their game doesn't work with the new engine, I tried.