I know this is probably a very easy question, but I've been googling for hours and I can't figure this out.  How do you upload a new version of a file?  Hopefully I'd like to be able to do this within a custom object that has a related list of files.  But I can't even figure out how to upload from the actual file.  Everything I've read says that there is a button called "upload new version" and I can't find that button anywhere in Lightning or Classic.  Attached is a screenshot.  Can someone please help?

Simple question.  On an Opportunity you can upload files.  I want to query the upload file object and check what files were uploaded.  What is the object name to query?  I've been looking for an hour and can't find it.