Both 7050 tower and SFF have dedicated 2.5 sata bay.  You can install 2.5 ssd in there. You do not have to use 3.5 to 2.5 adapter to install 2.5 in 3.5 bay.

M.2 ssd uses standard M2 x 3mm screw.

In case You'd like to insert 2.5" SATA SSD:

If You have an SFF, and only have a 3.5" Caddy then You need this to replace the 3.5" caddy:

https://www.ebay.com/itm/164916319512?epid=1074439820&hash=item2665c75518:g:XRwAAOSwEbNgym~7

or this, but then this inserts into the 3.5" caddy:

https://www.ebay.com/itm/174766534870?hash=item28b0e5b0d6:g:8vkAAOSwnZ5gm89V

But You are better off with a 2280 M.2 SSD.

You don't need a screw for them, because they come with a light blue plastic "thing" that replaces the screw. Just pop the lever up, insert the SSD and then plug it in again.

You could have NVME or SATA SSD-s in the M.2 slot.

Both work fine. Obviously there is a speed difference, however the SATA M.2 SSDs don't get so hot as an NVME.

If You have an MT, then for inserting 2.5" SSDs You need this (can have 2 of it):

https://www.ebay.com/itm/202676729444?epid=2168630497&hash=item2f30797664:g:sQkAAOSwodhc11PO

Thank you for your replies.

I see the blue plastic plunger thingie of which you speak, opposite the nvme slot. Looks the right distance away from the slot for a 2280, so it takes the place of the screw in some other Optiplex models.

But is everything 100% compatible with a m.2 nvme SSD? I believe the slot was originally intended for Optane memory.

And also, do I need to purchase a heat sink for it? I don't see one.

Thanks again.

It's totally compatible with an m.2 NVME SSD.

Don't have to buy a heat sink for it, but it's nice to have.

You can attach that later.

When installing Windows onto the SSD make sure to select AHCI instead of RAID in the BIOS setup.