SketchUp doesn’t have a Transform menu like in Adobe Illustrator, unfortunately. Drawing a line and scaling your object based on that line is one way.
You could also use the Tape Measure Tool to scale your entire model uniformly. Refer to the following video from SketchUp’s official YouTube channel - SketchUp Training Series: Tape Measure Tool. Have a look at 1:45 for the exact process of scaling with that tool.