Although it is not possible with Simplicity Studio, you can retrieve the data written in the flash memory by using the SEGGER J-Link commander. J-Link is SEGGER's emulator implemented in the EFM32 starter kit.
Run the JLink commander (JLink.exe) from the command line and run the ? and press return to see a list of available commands. You can retrieve the data using the savebin command.

Data can also be retrieved using Silicon Labs' Simplicity Commander. SimplicityCommander is a tool stored in the following folder of Simplicity Studio v3.

• C:\SiliconLabs\SimplicityStudio\v3\SimplicityCommander

This tool can be used both in the GUI and the command line, but the data extraction function can be used only when using it in the command line. Use readmem for commands. The command to use is described as follows.

• Commander readmem --region @mainflash --outfile mainflash.hex

How to use Simplicity Commander (UG162: SimplicityCommander Reference Guide) is in the same folder, so please refer to this for how to use it. Also, please refer to the description below for help.

• Commander --help
• Commander readmem --help