You can calculate the conversion into different currencies from the following link
https://www.xe.com/currencyconverter/convert/?Amount=500&From=HKD&To=USD
Under Steam new rules, the codes are not usable in the Argentine region
Steam Wallet 500 HKD / About 64.34 USD Gift Card
After payment you will immediately receive a key Steam Wallet 500 HK
Steam Gift Cards and Wallet Codes are an easy way to put money into your own Steam Wallet or give the perfect gift of games to your friend or family member.
Steam Gift Cards work just like a gift voucher, which can be redeemed on Steam for the purchase of games, software, wallet credit, and any other item you can purchase on Steam.
Activation tutorials:
1. Launch Steam and login to your account
2. Go to Games, then click on the "Redeem a Steam Wallet Code " option
3. Enter the code and click continue
4. Funds will be added to your Steam Wallet