You did something super screwy to download the Adafruit BME280 library. Do this:
- Delete C:\Users\mjmil\Documents\Arduino\libraries\Adafruit_BME280_Library.
- Sketch > Include Library > Manage Libraries.
- Wait for download to finish.
- In the "Filter your search..." box, type "adafruit bme280".
- Click on "Adafruit BME280 Library".
- Click "Install".
- Wait for installation to finish.
- Click "Close".
In this case it was not necessary to manually download the library since it was in the Library Manager index. When you need a library that is not in the index, you can download it from GitHub by going to the main page of the repository, clicking "Clone or download", then clicking "Download ZIP".