One command to batch rename files to rescue lost pictures

There are too many pictures in the mobile phone, and eventually the Android error file is lost, and the lost folder in the system becomes a file named with a number without an extension. There is no way to deal with it under windows, and it can be displayed as pictures under ubuntu. There are thousands of files. Use the following command to name the files in batches,
rename 's/$/\.jpg/' *
haha, I have seen linux Great power, my pictures are back.