One thing I find useful is to set the model units to meters and model in either inches or millimeters as needed. So if I need something to be 6mm long, I model it at 6m long. Since .stl files are unitless modeling in meters is not a problem. Export the .stl file in meters (model units) and import it into the slicer software as millimeters or inches as appropriate. Working in meters will allow you to increase the number of sides for circles and arcs. Keep in mind there's no point in overdoing the number of sides you choose.
Example: This was modeled at 63.5 meters tall. Imported into the slicer at millimeters and presto!
Screenshot - 1_13_2020 , 1_12_09 PM.png
By the way, your profile says you are using SketchUp 2019 Make which does not exist. Which version are you really using? That information is useful to those who would try to help you with your questions.