Yes all cables plugged in and the graphics card is plugged in too as I read that the amd ryzen processer won't boot up without the GPU.It won't do any harm trying the 3350 but depends if its supported (bios), which motherboard did you get ?
All power cables plugged in the 24 pin and 8 pin
This is the motherboard I got:
Gigabyte A520M S2H