Help needed with the Portfolio post type

Hi! The "Portfolio" page, which appears to be auto-generated by portfolio post types, is working fine but we would like to add the individual portfolios to a drop-down menu. In the Wordpress menu editor, the individual portfolios don't appear as either pages or posts. Any idea on how I can get the individual portfolio posts added to a drop-down menu? Here's a link to our current portfolio page: https://www.birthandbeauty.com/portfolio/ On that page, you can see three portfolios listed. We would ultimate want to change the current "Portfolio" navigation menu to a drop-down, with each portfolio, shown on the page, as a drop-down menu item. Thanks in advance! Peace...