CDs make for dubious long term storage (just Google "storage life CD" or a similar term). In addition to degradation over time, the data are stored on the thin layer of film on the top of the CD, so it's very easy to damage. There are lots of reports of very old CDs still being readable, but it's not something I would rely on for any data of importance or sentimental value.
Stick the drives in non static bags, bubble wrap them. If you are paranoid, use cheap Pelican-style cases and desiccant bags.
If they are older style drives with the IDE interface (Google it), then you might want to copy all the data to a newer SATA drive otherwise you're likely to run into plug compatibility problems in the future.
Edit: a quick search shows much higher lifespan rates for writeable optical media than I recall from just a couple of years back. Not sure if something has changed in the technology? Anyway, I still wouldn't use them due to the small storage capacities and ease of damaging the data layer. I'd personally stick to a couple of duplicated HDDs if I was trying to keep it simple and cheap, and copy the data to new media every 4-5 years anyway.
> also is there any good place in HK who can do data transfer
> from hard drive to CD?
For any reasonable size drive, you are going to end up with a zillion CDs. Say you've got a 100GB drive- that's over 150 CDs, or 25 DVDs. Just stick with hard drives.