HELP so I don’t mess things up: Backing up emails by copying MBOX files in Library>Mail?

Hello, I might actually use some assist so I don’t by accident delete years value of emails.

I use Mail.app for my e mail shopper on macOS 12. I have gigabytes of emails sorted into dozens of folders in the app. Since these are IMAP messages, they’re additionally taking up gigabytes of my on-line e mail storage. I’d wish to export these folders (which embody subfolders) from Mail.app in MBOX format after which retailer them on an exterior drive after which delete the emails from Mail.app and the net e mail server.

1. I see in Library>Mail>V9 all of my folders in Mail.app are already saved there in MBOX format. Can I merely copy and backup this “V9” folder, and can that give me copies of MBOX files that I can then import into Mail.app in the longer term (if I have to)?
2. Or should I manually export each folder in Mail.app as an MBOX file?

Simply backing up the V9 folder is clearly a lot faster since I will not have to manually export each folder as an MBOX file, however I’m unsure if these MBOX files already in the folder are your customary MBOX files with all my emails and attachments?

I would actually admire any recommendation with this. Thanks.