Media queries & Hamburger Menu

Hi, I am building an external non-WordPress page to link with https://hotelprairie.com It recreates the look & feel of the parent website and I am trying to emulate the transition to the mobile hamburger menu. I see quite a few media queries in the CSS, but I haven't been able to locate the code addressing the swap between the horizontal and mobile menus. Please point me in the right direction. thank you