It looks like all the RetroPie images moved under arcade punks.
The 3B+ is slightly different from the 3B so one of the images that said it would work for 3B didn't work for me.
So here's the steps to get it working...
Get the stock RetroPie Image from Raspberry Pi Imager
. Note the new version doesn't let you drop in the wifi info on install which is kind of annoying and makes the initially ssh setup harder.
Install to the sd card.