Q: Currently I have 'on my mac' mail boxes (in MAIL) and I have folders and mail boxes in iCloud.  How do I transport all the folders/mail boxes from 'on my mac' to iCloud?

Are the mailboxes you are talking about belonging to other email accounts? You can't get iCloud to receive mail from other email accounts. However if you have 'On My Mac' mailboxes which contain emails you can move these (or their contents) to iCloud easily enough. For each mailbox:

1.Create a new mailbox with the same or a suitable name on iCloud.

2. Open the mailbox you want to move.

3. Hit command-a to select all the messages.

4. Click and drag on any of the messages to move it to the new mailbox in the sidebar.

5. If there are a lot of messages, take the dog for a walk because it's going to take quite a long time as they all have to be uploaded

If you have a very large number of messages don't try to do them all at once.

Hi, please could you help me - am I able to use command-A or a simialr command to select all the MAILBOXES and have them move over rather than creating individual mailboxes and having to go through the process for each mailbox ?Thanks

Command-A won't work: you would need to click the top one and then shift-click the bottom one to select all. However I don't know whether you can actually move a whole mailbox so I should try it with one first. You may have to create each mailbox and upload the contents. In any case I shouldn't try to do too many messages in one go because it might fall over. If you have a lot of messages it will take a long time as it is.

In my experience that method usually fails.