Thanks for your advice.
I use a Samsung power supply for my mobile phone S6, output 5V 2A, to run Raspberry Pi3 B. It works without problem.
This is only a test on Raspberry without practical use. I have powerful desktops at home, AMD 8-core PCs with 32G/64G RAM installed.
I have old internal HDs such as 1T/1.2T WD, black label, and ADATA 120G SSD here which are installed on PCs for old data storage.
I have made some search on Internet. To connect an internal HD to Raspberry Pi I need to convert it to external first which I need to buy a kit as shown on following video;
How to convert an internal hard drive to external (easiest way)
But to connect an External HD to Raspberry Pi I don't need the abovementioned kit as shown in following video
Raspberry Pi 2 External Hard Drive Installation: Part 3 - a Step-by-Step Guide!
Rather than to buy the kit for one time use I'm willing to pay more to buy an external SSD HD which I can use in my internal network later for storage. That is the complete story.
Suggestion would be appreciated. Thanks