@top-specci a pi 2 image will work on a 3b+ as long as it's an image based on raspbian stretch. If it's an older retropie version then it will not work on the 3b+.
Contributions to the project are always appreciated, so if you would like to support us with a donation you can do so here.
Hosting provided by Mythic-Beasts. See the Hosting Information page for more information.