UART from nrf9160 to nrf52840

I currently am using a nRF9160DK. I want to have the nrf52840 on it scan for BLE devices and return the device count and then send this over UART to the nrf9160. 

How can I do this on the nrf9160 side? The codes I have seen don't build for UART connection. 

Any suggestions appreciated. New to nRF SDK! 

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