How attach dll for debug release versions x64

Hello, I have got a c# Class Library, .Net framework is 4.7.1. This library uses dll files with different CPU configuration and Build settings.
Actually, I use the x64 version and set project configuration (.csproj file) according to debug/release building like this:.\dlls\debug\dllName.dll.\dlls\release\dllName.dll After building, it, I want to use these libraries in my Windows Unity project. But I have got a lot of problems with it.
First is - I can't set CPU configuration for unity VS project - there is ANY CPU only, how can I change it (when I change it and close VS, after opening it's ANY CPU again)?
Second is - How can I set Unity to use debug/release versions of my library?
The problem is that when I try to build the application it throws an exception that unity can't use or can't find dllName.dll. Help me, please