SAS vs SATA.. worth swapping / can I swap to SAS?

New to this world!

I My ‘workstation’ is a hp z820, dual xeon (e5-2680v2) , 32gb ram, and:

internal drive (3.5")2x 1tb HDD2x 2tb1x 4tb

1x 1tb nvme1x 256gb ssd2 x 128gb ssd

This workstation gets used for data analysis, crunching and optimisation of data sets, and for web, illustrative design and creative use, movies sometimes.

I also have 1x 3tb drive, 1x 4tb drive.

The ext are USB3, I have since heard about shucking, noting that I don’t have the room in the tower for those anyway.

All internal drives are Sata3, with the NVMe drive on a pcie 4x adaptor.

Should / Can I convert these data drives into SAS drives using converter cables?
Can you do that? Why would you do that?
I would need a SAS card to do this.

Is the main point in using SAS card/converter cables for the use of a DAS (direct attached storage)?

Currently, I am running windows but had a storage space pool, which actually failed the other day.
Thus, I created this thread: first post about OS/software