Musical notes are a base-7 system denoted with the letters A-F repeating. Given that it is not a numerical system, different A's or B's (ect) are marked with numbers rather then continuing like hex. i.e. A3, E5 (etc) with lower tones being lower numbers.

To answer your question, you won't. Perfect pitch usually develops in people who have had musical training since very young childhood. Just like you can't really remember learning your native language, they can't remember learning this skill. But like everyone, they did learn it at some point.