Source for preflash unclear

This page https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK/GetStarted says "If step 4) below fails, you need to re-program the factory example code into the flash. Click here for instructions." and clicking the link goes to this page https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_nrf5_v16.0.0%2Fpreflash_example.html&cp=6_1_4_6_23 which says "You can find the source code and the project file of the example in the following folder: <InstallFolder>\examples\peripheral\preflash".  It is not clear/evident where to find the folder described.

Please advise as to where I can find the factory example code to reflash the DK. 

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