File conversion for Photoshop 2020

Hi,

I am unable to open my purchased files in Photoshop 2020. Am working on a Mac. I requested a file conversion but have received no further information from the artist.
The files did not download grouped (zipped) so possibly that is an issue?
Have attempted to follow several suggestions that suggest opening the .obj or the .mtl but this does not work.
Any suggestion on what to do?

Thanks!