I have been using the Quest app thing to make my gamebooks instead of making them online. They are saved in the form of a .aslx file, and I cannot upload them because they aren't .cas or .Quest files. Does anyone know what I may do to resolve this? I really don't want my work to be wasted, I have put so much work into making these games.

Publish you game....
First item under tools.
That will convert it to a .Quest file.