Powering a pro mini and LED strip

Projects General Guidance
1

I'm making a motion activated LED strip as night light but I'm not sure about the exact power wiring
Replacing the UNO with a pro mini (5v) and with a 12v led strip and a 12v power supply I fried the board last night. Not thinking clearly, I ripped away the wires before checking it. But most likely I messed up the grounding. (And yes, I connected the 12v to RAW).
I got a new board and this is how I plan to wire the power:

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But I'm thinking of using a buck converter for 5v, like this:

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Does it matter which side of the buck converter I ground the parts?
I would be grateful for any comments.

This is the original circuit and it's source:

2

What parts exactly and what do you mean on which side?

I have had some buck modules with voltage in, voltage out, and one ground " for both"

3

You mostly messed up the connections to the MOSFET.

Gate not connected to D9.