8.2.1s200 is the special firmware released to support the C-Band prior the 8.3.0 firmware release.
If you have go through the cell module firmware upgrade using the firmware 8.2.1s200, nothing need to be done for your device after you have upgraded your device using firmware 8.3.0.
For those devices that is not using the firmware 8.2.1s200 , they just need to perform the same like 8.2.1s200 after they upgraded the device using 8.3.0 to upgrade the cellular module firmware and it will allow the device to support C-Band connection.