What reports are you talking about and in what folders are those reports?

Firefox uses two locations for the Firefox profile folder. Location used for the main profile in "AppData\Roaming".

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

Location used for the disk cache and other temporary files in "AppData\Local".

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>\

I found them by opening Firefox\open menu\help which took me to the file path you have indicated that goes through Roaming. That path ends in a file 31hiduik.default. In that file there is a folder called datareporting which contains a folder called archived. That folder is full of dated folders which in turn contain lots of Java files. I have two concerns. The first is, what data do these files contain and secondly, is there any need to keep any other than the current year folder.

I have an idea about the files with crash in their names, but the others, I'm not sure. You can turn off "Health Report" (and if it's turned on, "Telemetry") in the Advanced Options and see whether that affects what is stored in the folder. See: Advanced panel - Accessibility, browsing, network, updates, and other advanced settings in Firefox.

The files in the archived folder are compressed with jsonlz4 compression in the same way as the automatically created bookmark backups in the bookmarkbackups folder. You would have to decompress them to check their content. I'm not sure if you can disable creating these files in the archived folder as I still see them with profiles used by Nightly builds that have most datareporting prefs either locked or set to false although most deal with health report.