search for file extensions with ~ in finder
In Finder hit Cmd+F to open the Spotlight interface (without requiring a string to search for).
Hit the search parameter dropdown (by default "Kind"), select Name.
Select 'matches' in next dropdown.
Type tif~ in the text box.


You could select Kind → Other and insert tif~, but does not work that way.

Additionally,  you could search for it on the Terminal type the following in your home directory:

find . -name "*.tif~"