I migrated music files from my old Mac to my new Mac but I don't have the permissions to open the folder with the new files. The option to select the folder with the transferred files was grayed out when I used "Get Info".
It does not sound like you are comfortable with using the command line so here is a GUI based solution that you might try:
If you are able to
Get Info on the folder of interest go the the very bottom section
Sharing and Permissions.
By default this section is greyed out for all files/folders regardless of the owner/permissions. You can gain access to this area by clicking on the lock ion in the lower right corner of the
Get Info window.
Once you have input the admin password for the computer you should be able to edit the permissions on that file/directory.
You can recursively apply the changes made to the permissions by selecting
Apply to enclosed items from the gear shaped dropbox in the lower left of the
Get Items window.
If you are familiar with the command line there are alternatives to this approach but give the graphical method.
Click "get info" for the folder/file in question and then in the window that opens, look at the bottom right of it.
There should be a padlock item next to the file permissions area. If the padlock is displayed in the "Locked" position, then click it ones to 'unlock' it, then the file permission sections should no longer be greyed out.