Arduino - Windows can't find the drivers
You may not have installed the drivers when installing the IDE. The only way I know to reinstall the drivers is to reinstall the IDE and make sure when you get to this screen you tick every box:



Otherwise you may not have selected your board correctly. To select your board in the IDE, go to Tools > Board > Arduino Uno/Genuino Uno

Your port select may then appear, it should be COM1 or something similar. If you have multiple, just try them all by selecting one and then upload a sketch to it. The Arduino Uno should flash some lights if it worked correctly.