Trying to rename files based on file size

I am trying to rename some MP4 files based on file size of mp4 files in another directory. I want to name all files with identical sizes to same name. Meaning if the file size of the source file matches the size of file in the comparison directory, the source file is renamed to whatever the compared file is named. Can AR do this? I can also make a list for comparison with the info in it in 2 columns by using the DIR command in windows giving me a list like 123456789 movie.mp4 (this might be better method since comparison directory needs to be read recursively)...can someone tell me please - Is this possible?

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