Hello @Saimanoj 

There is no way to move data from one mount path to an existing mount path, but if you want to move it to a new share you can use the Move Mount Path operation.

https://documentation.commvault.com/11.26/expert/9302_moving_mount_path.html

A way to “pseudo-move” existing data to existing mount paths is to disable the mount path you want to remove for new data. This will have subsequent jobs re-baseline the existing data on the remaining mount paths while allowing backups to age according to storage policy retention.

You may also want to prevent block references to speed up the process.

https://documentation.commvault.com/11.26/expert/9376_disabling_write_operations_on_mount_path.html

This is a long post - but should have the answer - its worth a full read

Towards the end you should see a write up that could address your issue

I've extracted it in italics below

So … I misunderstood the instructions for Moving a Mount Path which say:

• The move mount path operation overwrites the destination mount path. Therefore, ensure that the destination mount path is an empty folder.

I mistakenly thought this meant I couldn’t move to one of the existing drives but it turns out that all I needed was to create a new folder.  I created L:\MP4 and was able to move everything off M: to that new folder so I’m in a good position to change the configuration on the M: drive.  Thanks everyone.  @YYZ was correct and I’ll mark their reply as the solution.

Ken