how to offload contacts through USB?
I recommend one of these two free Android apps, both of which I find easy to use:


Red Rock Backup Contacts, which exports to Google CSV, Outlook
CSV, or a custom CSV, and has no builtin restore (You can easily
restore using Google Contacts).
OBSS MCBackup exports to vCard
(one file per contact) and does have builtin restore.


Both of these apps export files that can be imported into most contact managers (not just Android ones). Also, both of these can email them to you if you are having trouble with your USB connection.

Note that files created by these apps, like all Android files, are subject to a bug where you may need to restart android before they are visible over MTP to transfer to your computer.