mp3 On my car not working downloaded with Mac

I'm guessing you have the same issue discussed in another thread.

When the Finder copies files to a non-Mac filesystem, it will create hidden files to contain file system metadata that doesn't exist on non-Mac filesystems. So you get something like

SONG1.MP3
._SONG1.MP3
SONG2.MP3
._SONG2.MP3
SONG3.MP3
._SONG3.MP3

The files whose name begins with "." are not MP3 files. "." is a Unix convention for hiding files, so on a Mac, these files are hidden from directory listings unless you specifically ask to see hidden files. The "._" pattern is just a way of creating metadata files with unique names that are clearly associated with their main .MP3 counterparts.

Unfortunately, many non-Mac systems just see the .MP3 and think the ._*.MP3 files are corrupt MP3s. There may also be some other files with leading "."s that the Mac Finder will put onto a USB flash drive.

The solution is to clean the unwanted files off. (Even if you clean off the extra files from a USB stick that has MP3, AAC, or JPG files, and later copy the files back, you don't really lose much.)

The other thread goes into more detail about this. I'll see if I can find it.

Here we go:

Problem with Music Files on USB Drives - Apple Community

You can fix it by issuing a couple of Terminal commands as part of preparing a drive.

You can create a shortcut to run the necessary commands from the Menu bar. See the post from that thread's author:

"FYI... With big help from Barney-15E and MrHoffman (here and in the Lounge) I have created a Shortcut to delete all ._ files and all .DS_Store files and it works well from the Menu Bar …"

Ok I have try the same thing you have done and no mater what I tried it won’t work so unfortunately go to a buddies house who actually has a PC and build it on windows and I’ll work 100%