Nuka World DLC question (Fallout 4)

Probably the plot.

vlad1083
There is a power plant somewhere and if it is captured everything will be

Kirill_Shvarev
actually there is one "but"
I cleaned the power plant and found a control station on the roof where you can turn on the power (as I understand it)
but the door is locked with a key that needs to be found (the door cannot be broken) the
question is - where is the key ??

1SkyBow1 44176
I don’t know, it appeared in my inventory myself.

1SkyBow1 44176 You can
open the door by moving through the DLS storyline, either as raiders or merchants.