I can connect same sensor using nRF connect app. See attached snap shot.
The BLE connected Pressure sensor is advertising the Unknown Service using UUID : -- 18FF (First Image)
using this UUID I am able to pair same device with nRF52840-DK board.
Now I want to read Value of unknow Characteristic using other UUID from Attribute Table. (Second Image)


which function or API will be used to read these values ?