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This is a configuration that Intel has not validated with this NUC because it was done and tested basically for SSDs.
In this case, for you to get enough power to the HDDs you will need to purchase an external power supply for the HDDs, a hub or something similar that can provide enough power to the HDDs.
In this case, if somebody has already tried this configuration with the NUC is free to share it with us in order to help you.
Unless this drive has additional requirements beyond the standard 2.5" drive, you should be able to power your 2.5" HDD via the power connector provided on the board. You will definitely need a separate power supply to power the 3.5" HDD, however.
I suggest that you connect the 2.5" HDD to the onboard SATA connector and test it standalone. The 3.5" HDD can later be added via the M.2-to-SATA adapter. You can adjust the Boot Order table in BIOS Setup (Visual BIOS), to ensure that the 2.5" HDD has precedence over the 3.5" HDD (regardless of SATA port assignments).
Hope this helps,
The typical 3.5" HDD requires ~20 watts to start up and somewhere between 6.5 and 9 watts to operate. Further, 3.5" HDDs require power to be provided via both 5V and 12V inputs. The Orange USB 3 Charging port provides only 7.5 watts and this via a single 5V input. You just aren't going to get there this way.