TIMELINE QUIT SHOWING FILE IMAGE, CHANGED TO SHOW FILE NAME

THIS IS PREMIER ELEMENTS 2020 ...On my Premier Elements 2020 my Timeline just changed...It is NOW showing only file name; i.e., IMG_0000.  This happened before, I found steps to change back to images, but now can't find.  Can someone please help me to change it back to file thumbnail IMAGE?  

THANK YOU so very much if you can