I think sketchbook exports everything as a .png file. I would try copying, not exporting, the file to a computer, then copying it to your new phones autodesk/sketchbook3 file. If it doesnt show up in the app after that, go to gallery(through the app), hit the + button, new from image. Then navigate to your autodesk/sketchbook3 folder, it should be the last modified .tiff, pick that one. You might write down the file name just to be sure, since sketchbook doesnt seem to save files with the names users give them.
Hope that helps
