M.2 SSD upgrade

Yes, as you can see from the storage specifications link below, PCIe NVMe SSD is compatible with your OptiPlex 3080 mini tower.

https://www.dell.com/support/manuals/en-us/optiplex-3080-desktop/optiplex3080_mt_specs/storage?guid=guid-2435e70b-2792-4c78-9904-a3f5cb928e46&lang=en-us

PM961 256 GB SSD is validated by 3080 user

https://www.userbenchmark.com/UserRun/56845922

@Chino de Oro​ Hi Chino, PC at present boot from the 3.5" drive, if I install this M.2 SSD will the PC still boot from the 3.5" drive or I have to fresh install windows in the M.2 SSD?

If you install an M.2 drive, your system will still boot from 3.5" HDD.  But, that will defeat the purpose of wanting to take advantage of M.2 NVMe drive performance.  You may want to perform a fresh install on the new M.2 drive and boot from there.  Delete all partition on the 3.5" HDD and use it as storage later.

Any important data must have been backup externally.

Will the installed M.2 become automatically detected and configured as the primary drive or need to be configured in the BIOS to set as the primary booting drive?

Then to fresh install windows on the installed M.2 or clone windows from the 3.5" to the installed M.2

then as in your message the 3.5" can be used as storage?

No, the M.2 SSD will not active until you go to Disk Management and initialize it (except if it's a used drive with OS on it).  You can not boot from M.2 until installing operating system on the new SSD.

Performing a clean Windows installation or cloning from existing boot drive is up to you as user preference.  The same if you choose cloning, remove the 3.5" HDD and test boot with the new M.2 SSD first.  Until you are satisfy that there is no performance issue, reinstall the HDD and select F12 at boot to select boot from M.2 SSD.  Then using Diskpart to clean the HDD, then set it up as storage.

In the setup and specification page the following sentence say that (

• with a M.2 solid-state drive, the M.2 solid-state drive is the primary drive)

At present the PC boot from 3.5" drive, what expect to happen if I install M.2 SSD? will the PC still boot from the 3.5" until I install and configure the M.2 SSD?