M2 is a socket not a slot.

A and E keyed M2 is wifi only

B & M keyed m2 is SATA

M KEY only is PCI-E and requires 128b/130b line code.

So you are limited to SATA B & M keyed storage.

15MCR - Dell X400 512GB SATA 6Gb/s M.2 2280

https://www.amazon.com/Crucial-MX500-500GB-2280SS-Internal/dp/B077SQ8J1V/

Thank you for your answer on the mother board it says slot sorry.

However as you can see it has just one key instead the memory that you suggested has 2 key

it is correct?

I am very confused about m.2 sata nvme atc atc :))

M2 Keys are not linear or identical.  The wifi socket is A and E keyed which means you cannot put M2 storage drive in there EVER.  M2 is a socket not a memory/storage/drive specification. SATA Based M2 drives work. The others do not. These 2 standards are NOT interchangeable.  They are both M2 but not both compatable.  YOU MUST USE M2 drives that are SATA with 2 keys.

Its 5 pins and 6 pins on either end so that you do not FORCE insert B&M keyed drive backwards.  Keyed  to try and prevent gorilla grip hammer in the forhead forcing in the wrong way but it wont prevent it from destroying your M2 drive if you FORCE it in.  Your keyway is 5 pins wide

I

M2 Keying

I am having problem to explain in english what I mean

I try to exaplain my doubt with an image that I did.

The memory looks to have both key but motherboard just M
So it is compatible?

B & M Key is sata so its fine. 

That does not partition and format the machine however.

You have to install OS with BIOS Sata operation set to AHCI

ok thank you.

The last question is about the speed.

Do you think there is an increase using socket m.2 sata instead of the sata 2.5??

sata drives are 600 meg max. Again you mistake M2 for a storage standard its not.  SSD gives 450 meg average vs 130 meg Hard drive.   600 meg is theoretical speed not guaranteed performance.

You can even convert the M2 SATA drive into a 2.5 ssd with an adapter.

https://www.amazon.com/LWS-Enclosure-Adapter-Converter-Support/dp/B07WN4KV64

https://www.google.com/search?q=m.2+ssd+speed&safe=active&client=ms-android-americamovil-us-revc&sxsrf=ALeKk00TnMBc7UAr_AaJupPlS71ht-Cv8g%3A1623986362376&ei=uhDMYPq8FpjWtQaV0qXwAQ&oq=m.2+ssd+speed&gs_lcp=ChNtb2JpbGUtZ3dzLXdpei1zZXJwEAMyAggAMgIIADIHCAAQhwIQFDICCAAyAggAMgYIABAHEB4yBggAEAcQHjIGCAAQBxAeOgQIABBHOgcIIxCwAhAnOggIABAIEAcQHjoECAAQDVCyqQJY2rsCYIW-AmgBcAF4AIABdYgB_ASSAQMxLjWYAQCgAQHIAQjAAQE&sclient=mobile-gws-wiz-serp 

https://www.google.com/search?q=m.2+sata+speed&oq=m.2+sata+speed&aqs=chrome..69i57j0i22i30l4.8628j1j7&client=ms-android-americamovil-us-revc&sourceid=chrome-mobile&ie=UTF-8 

9020 micro does not support PCI-E M2 SSD's so the higher speeds are not an option.