Itunes Country Code Tag

Hi everyone,

Hoping someone can help me add the country code tag to m4a. I have tried using ItunesstorefrontID , but to no success. I now the six number code for the us is 143441 but I can't seem to be able to add it. I use mediainfo to check if the tag works

Please help

Find a file that already has the country code.
Load it into MP3tag.
Open the dialogue "Extended tags" (Alt-T) and check if the field appears in the list of fields.
Then use the name you find in list.
If you do not find the field then MP3tag cannot edit that field.