Audacity and mp3

Hi, there. I am new and will try to learn as fast. I have a quick questions. After I record and edit a voice file using Audacity, can I transfer the file to an mp3? Are Audacity and MP3 compatible. And also, in order to store about 3-4 hrs of voice files, how much memory do I need for an mp3?

Audacity can import (open) MP3 files, but due to patent issues it cannot be shipped with support for exporting (saving) MP3s. However, if you install “LAME”, it will add support for exporting MP3s to Audacity.
See here for how to download and install LAME:

The actual size of an MP3 file depends on the compression settings and audio format as well as the length. Typically an MP3 file will occupy around 1 MB per minute of audio (disk space).