What is file extention .ext,

My WD backup says 4 files fail to back up. WD has them all ending with the extension .ext
The names are a combination of about 30 letters that mean nothing to me. They are all 32kb. What are they?.
How can I find them on my computer?
I need to either delete them or if they are important keep them.
If I keep them WD will continue to say they failed to back up. .
Any ideas would be helpful.
Linda

Hello,

Please refer to the following KBA article: https://support-en.wd.com/app/answers/detail/a_id/8701/