Converting .gp5 files directly to .midi format.
Converting Guitar Pro 5 Tablature Files directly to MIDI Music Data (.gp5 to .midi conversion) is quite straightforward, and certainly possible using the actual Guitar Pro program. It allows users to export tablatures, but also MIDI audio files.
You will, however, need the correct Guitar Pro version, as the .gp5 file type is associated with an older version of the software. This file type has been replaced by the .gpx format.
Alternatively, you may want to try certain third-party utilities, such as MuseScore, also supporting a wide range of formats.