For the SCH-R530U, a stock ROM is not one file, but a trilogy of official Samsung packages, each serving a distinct purpose:
You can download the stock ROM for your Samsung Galaxy S3 on US Cellular from the Samsung website or other reputable sources. Make sure to select the correct model number and firmware version for your device. samsung galaxy s3 us cellular stock rom
Download and install the Samsung USB Drivers on your PC. For the SCH-R530U, a stock ROM is not