When looking in that Mods folder you should see a directory called Ana_Vehicle_Respawner. If you aren't seeing that then that would be the issue. When extracting the file from GitHub it makes a zip named 7D2D-Vehicle-Respawner-A21-main. So when you exact that with windows it can put that as the top folder and it not the one you want to be top folder. You just need to go into that folder and copy over or upload the folder Ana_Vehicle_Respawner (and all the files included in that folder).