Create nuget package with multiple DLLs And text files

i am creating a nuget package locally using nuget.exe package was created successfully but while referring the package through nuget it will show error in output window of visual studio.My Package does not depent on Any framwork and i did not add any dependency of framework

Could not install package 'Package.x64 1.0.0'. You are trying to install this package into a project that targets 'NETFramework Version=v3.5', but the package does not contain any assembly references or content files that are compatible with that framework.