Is your goal to make a nice rendering, without having a physically-representative model of individual floorboards? To make a nice rendering you can probably find on-line a repeating-tile texture image that has a hardwood-floor appearance (which covers a 3x3 foot space, say), and then apply that as a “texture material” to a single large rectangular face in the SketchUp model.
If you want to model individual floorboards, then it would be fairly simple to draw a basic floorboard as a right-rectangular prism shape (using the Rectangle tool and then the Push-Pull tool). This assumes you don’t need the tongue and groove features of the floorboards (but they would also be simple to create). With a prototypical floorboard component, you could copy it lots of times to create sufficient instances of the component to fill the room. Use the Scale tool to change the lengths of the instances for variety, and to fit them up against the walls. I’m not sure the best way to apply a wood texture image to each individual instance, or if you would be OK if they all had the same texture. I think there is a way to prevent the texture from stretching when the size of an instance is changed via Scale, but I haven’t used textures with SketchUp.