The reason they've disappeared is that you have far too many emails in your Inbox and Deleted folder. If you want to keep all the messages in the Inbox then create archiving folders (as sub folders of Local Folders) and transfer them to there. Also delete all messages from your Deleted folder. If you do this then the missing messages should re-appear.
Windows 10 Home vs Windows 10 Pro comparison: Here are the extra features you get in the Pro version