The best way to burn an image to an USB Key / SDCard is using the application balena etcher:
Step 1: You can download it from its official download page and then open it on your computer.
Step 2: Select the image file you wish to burn to your SD card. To do this, click Select image button and then locate an image file from your local drive.
Step 3: Click on the Flash button and wait until the process is complete.