DELL-Sandeep PHi SobeNirvana,
Thanks for providing us this information. I would like to inform you that on our motherboard Front Panel Connector is at number 12 on the above image.
As you have replaced the motherboard it might be different on your system. Kindly refer to manual or documentation that came with the motherboard.
And if the motherboard doesn't support the power switch then it would be better if you don't install it, as it may cause damage to the system.
If you have any further queries, please feel free to contact us.
Thanks and Regards
Sandeep P
#iworkfordell
As OP mentioned - motherboard was not replaced! Computer case was replaced. Dell doesn't have RESET button, so this one is extra.