As a generic rule, quarantine should be one folder and the file should be there, but with a different name. And looking by content may not help. However, since you know the size, you would have to copy the file to the original location. (Of course, the first step is to whitelist the folder. @BitCryptex already wrote that.) Also there's a tutorial on Avast Quarantine on their website.

If the file is not there, maybe it was deleted. In this case, for your safety, the best is re-download with Bitcoin Core.