How to transfer backups on Windows Server if they exceed a certain amount?

Question

Backup

There is MSSQL server 2012 and an 8 terabyte disk. We make backups according to the rules. Shelf life 6 months. Somehow we want to come to the conclusion that if 7 TB is occupied, then transfer old backups to another disk automatically.
bak files, the oldest ones must be transferred to another disk if there is 1 TB left on the current one.