short code for a specific portfolio category and its items

I tried to make a portfolio specific category page as a sub-menu under the main menu links however it would just make the category page part of the main menu. As a work around, I thought I would just make a new page with a short code added to the page to link to a specific portfolio category with it’s portfolio items however I don’t know what the short code would be.

If I have 2 categories in my portfolio called OMDE 601 and OMDE 603 and I want a page as a submenu that when clicked will take me to the page that lists all my OMDE 601 portfolio items. Well that is what I want to do but don’t know how to get there. Thanks.

Jeff