The .ORI file extension is often appended to existing file names to indicate that it is the ORIginal file.

For example, if we have a two files in a folder:

mytextdocument.txt
mytextdocument.txt.ori

You can probably safely assume that the file with .ori appended is the original version.

You may need to remove the .ori from the file name to open the file. Remember, you can't have two files with the same name in one location, so you'll need to either move the other file to a different location, or rename them.