Failing in release

[shivareddy37]

when running "cmake -DCMAKE_BUILD_TYPE=Release .."
I get the following error

CMake Error at CMakeLists.txt:6 (find_package):
Could not find a package configuration file provided by "Eigen3" with any
of the following names:

Eigen3Config.cmake
eigen3-config.cmake

Add the installation prefix of "Eigen3" to CMAKE_PREFIX_PATH or set
"Eigen3_DIR" to a directory containing one of the above files. If "Eigen3"
provides a separate development package or SDK, be sure it has been
installed.

I tried setting the prefix path like so
cmake -DCMAKE_PREFIX_PATH=/abs_path/FairMOT-cpp/third_party/eigen-3.4.0/ and cmake -DCMAKE_PREFIX_PATH=/abs_path/FairMOT-cpp/third_party/eigen-3.4.0/build

I still get the above error. If anyone could help new to c++