I have a mini 3 pro and use an SD card in it rather than the small onboard storage (i believe the non-pro does not have onboard storage). It saves the stitched jpg panorama onto the SD card in the DCIM folder, in the same place as all the normal photos/videos. When the option is enabled to save the 35 original unstitched images, these jpgs (or dngs) are saved in a numbered folder within a separate sub folder called "panoramas".
Maybe the mini 3 (non pro) behaves differently, though I wouldn't have expected it to. If there's no onboard storage, as specs imply, then the only place it can save stitched jpgs is on the SD card. It may be DJI decided to cripple some of the panorama features for the non-pro model.
There is no stitched JPG 360 Pano in the main folder. In the "Panoramas" folder, there are 35 DNG and 35 JPG.
Strange!