SOLVED

You cannot put a directory directly to a device or partition. If this write succeeds then your filesystem in that partition will be severely damaged and if you attempt it to a device then the partition table also will be destroyed.

Really ?
If I have correct permission I can copy entire folder from one partition to another using GUI.

The problem is Ubuntu "file manager" won't let me if I do not have proper permission, hence I have to use sudo / CLI and obviously not doing it right.

Let me rephase - how do I copy existing folder , not a whole partition, to RADI enabled partition?

You don't do that!
When you are attempting such an operation, you should familiarize yourself with structure and terms. There is a drive (block device), then it may have partitions on it, and for partitions to be useful they must contain filesystems. To access this filesystem for writing files it must be mounted. Your command has partition as target, it would make only sense if you had an image of partition, like a backup image. Same for whole drives, if you had an image of a drive then you could write it to a block device.

Let me try to make sense of what has been said.

Physical drives are devices.
On the device you can create one or more partitions
In the partition you can create (by formatting) a file system.

Once the file system has been created it may then be made accessible by mounting it to a folder (AKA mount point) on the system directory tree.

After the file system is mounted it may be accessed to read and write data to it.

That is the whole sequence to making a device capable to read and write files to it from an operating system

Now, a RAID device is treated exactly the same as a single physical disk. It is created from multiple individual devices and is then seen by the system as a single device. You have to create partitions, format file systems, and mount the file system before you can read or write data to it.

dd or ddrescue can be used to access the raw device but that is not the same as reading and writing file data.

A "RAID enabled partition" is not understood the same as a "RAID partition" although your meaning may be the same. I would understand a "RAID partition" to mean a partition on a raid device. If I have a raid device that has been partitioned already then I treat it the same as a partition on any disk.

A partition on the raid device has to be formatted as a file system and mounted. Then with the correct permissions you could use the gui to copy or move the folder to that new location.

I think one of your problems is not recognizing how or where to mount new file systems, and how to set the desired permissions & ownership of that new file system so your user can properly access it.

Once again I will point you to several basic tutorials that will help you learn all that.
Simply do a quick online search for "learning linux for free" or "learning linux online" and many different learning tools will pop up. Please spend a little time studying to help yourself in handling a linux computer better.