There are vacuums lines all over the engine compartment. The are plastic black lines that are the diameter of like size 8 spaghetti
Or they are black rubber hoses that connect from different things.
The vacuum lines connect to the intake manifold and to different devices in the engine compartment. The best way to check for vacuum leaks is to spray them with soapy water. If there is a leak, it will bubble there...or you can spray carb cleaner on the vacuum lines, and if there is a leak, the idle will increase momentarily.