You do this in the cr2 - open it in a text editor and replace the name of the path to the old geometry at the beginning of the file with the path to the new geometry. If theres a rpoblem like this I always try to figure out the cr2 file in a text editor.

Dont try this at random with other figures. In this case it worked, becaue the pants are "almost" the same in the legs and feet. The object of the Milpants has different materials and probably a problem somewhere. I got the idea from posts where morphs were not working.