Haha it made me laugh honestly when I've read about 20 years ago but let's get serious and that's probably just 2 years ago or even 10 years ago. Regardless of that,
They emailed me bitcoin address? and password.
If they have emailed you a bitcoin address and a password, that wouldn't make sense because there should be a specific online bitcoin wallet that requires you a password to log in and that's what you have to know or a private key so you can access your funds through a specific wallet.
I guess they were testing bitcoin in market and we can buy things in ebay with bitcoin.
I found old harddisk drive that probably has this old bitcoin.
Do you think we can still cashing out this old bitcoin?
You can still sell it for money as long as it's the actual bitcoin that we have. You need to clear more information about this and explore that old hard drive of yours.