The only jpeg to ttf conversion that makes sense, is not actually file conversion per se, but a process of making new font's based on pictures, or logos saved in JPEG format. This is doable with various font tools and typically used to make font files that contain a selection of pictograms and logos.
Another possibility is that this is just a typo for jpeg to tiff conversion, i.e. simple export of JPEG graphics to TIFF format.
Updated: October 23, 2023