is Base-16. It uses 0-9 and A-F to represent binary data. For example: 46 69 72 65 translates to "Fire" in ASCII text.
To start, you need a reliable hex editor. Popular options include: how to use hex editor to hack games
Most modern hex editors have a "Data Inspector" window (usually on the side or bottom). This is your translator. If you click on a byte in the Hex column, the Data Inspector will show you its value in: is Base-16