You need to move emails from one account or personal folder to a different IMAP account. You are using Outlook. You exported the “source” emails to a pst file and imported the file with Outlook to the “destination” account. Everything seems to have been done correctly because you see the folders of the old emails on the new account, however, inside the folders, you don’t see the emails.
Don’t be alarmed! The emails are there ….. but they are hidden
In Outlook, click on a folder where you don’t see the content. At the top click on View – Change View. In the window that appears click on “IMAP Messages“. If you have many folders in the same window, you have the “Apply current view to other mail folders” button.