I was using the original case designed by Dimwit-Dave for a pihole DNS server.
The Pi 3 B+ started getting too hot so I wanted to add in a fan.
I took the extended case lid remixed by jhuary and added in a 30mm fan grill. I connected it to pin 4 and 14 for continuous 5v power.
The fan I used is Amazon: B0792BW2VH and is 30mm x 30mm x 7mm at 5v.