How to install Opencv-Python 3.4.7.28 using pip

I tried to import cv2 for my python script but, there is no cv2 module. 
After some google search, I found that 
"python -m pip install opencv-python"
will works for me but, it installs opencv4 not opencv3. 
So, I searched google again and found that some conditions for pip command. 

$>python -m pip install "opencv-python==3.4" 
then I got this message:
ERROR: Could not find a version that satisfies the requirement opencv-python==3.4 (from versions: 3.4.2.16, 3.4.2.17, 3.4.3.18, 3.4.4.19, 3.4.5.20, 3.4.6.27, 3.4.7.28, 4.0.0.21, 4.0.1.23, 4.0.1.24, 4.1.0.25, 4.1.1.26)
ERROR: No matching distribution found for opencv-python==3.4

So I typed,
$>python -m pip install "opencv-python==3.4.7.28"
Collecting opencv-python==3.4.7.28
  Downloading https://files.pythonhosted.org/packages/db/97/7d04b67cfdc3588c38ed16c92c372a6f682953086b31fd7cefaa9a4a260e/opencv_python-3.4.7.28-cp37-cp37m-win32.whl (26.5MB)
     |████████████████████████████████| 26.5MB 1.7MB/s 
Requirement already satisfied: numpy>=1.14.5 in c:\users\sanghyun kim\appdata\local\programs\python\python37-32\lib\site-packages (from opencv-python==3.4.7.28) (1.17.3)
Installing collected packages: opencv-python
Successfully installed opencv-python-3.4.7.28