GI files are very old disk images from a long forgotten tool called Prassi and it's not surprised that people that find these disk images want to get it to modern standard like ISO, so the data can be accessed with pretty much any software. Your best option how to handle ancient disk images is to use ISOBuster, it supports pretty much any known (described) disk image format and is probably the best option how to export these files.
Updated: July 20, 2023