You do not sync your current pop3 account as such. Outlook 2007 will create a new inbox for every imap account. You can create sub-folders of each inbox and set up message rules so that e-mails are moved to the relevant sub-folder or to your old sub folders. But I wouldn't move to your old sub folders (file structure). The reason is that if you have sub-folder under the imap account then this is replicated on the server and automatically on every device (desktop, laptop, tablet or smartphone) that accesses it and all see the same structure.
iPhone X review