Leopard to Snow Leopard Mail Inbox

I'm having to manual transfer files from a G4 Mini running Leopard 10.5.8 to an Intel Mini running Snow Leopard 10.6.8. I've copied my Leopard User Files (Home Folder) to an external disk from the old mini, and now have the disk mounted on the new mini. From there I'm copying the files to the Snow Leopard Home Folder. In the Library folder > Mail, I copied my Leopard Mailboxes folder and that worked to get those mailboxes I had created into the Snow Leopard mail. However, I also wanted my old Leopard Inbox and Sent mailbox e-mails transferred into Snow Leopard.

Here's what I've done that didn't work. I'm hoping someone can tell me what I should do.

In the Home>Library>Mail folder, there's a folder called POP@(my e-mail addy). Within that folder is a folder named INBOX.mbox and within that is a folder named Messages. I copied the contents of my corresponding Leopard Messages folder into the Snow Leopard Messages folder, but the messages aren't showing up in my Snow Leopard Mail. (Note: I get my e-mail by downloading to Mail from my e-mail provider's website and it is immediately removed from their server, which I'm assuming has to do with the POP thing but is probably irrelevant to my question.)

Any ideas on how I can get my Mail Leopard Inbox and Sent box messages into Snow Leopard Mail?

I'm a novice trying to do this move from a very old mini and OS, to a marginally newer mini and a behind-the-times OS system. The reason I'm doing it manually is because of problems with migration assistant and changing from a G4 to and Intel.

Thank you!