Read your mbd manual
There was no reason to unplug the Sata cables
to change the Power supply.
Put them back where they where.
1 end goes to your hard drive.Other(S) to the motherboard Sata slot(S).
Read the motherboard diagram if you forgot where.
It's all in the motherboard manual or download a pdf version.
The monitor won't receive a signal,because your OS isn't connected.