Installing SSD in Dell Precision Tower 3420

Hello. 

I want to install an SSD in my Dell Precision Tower 3420.

I've reached what appears to be the SSD connector (see red arrow), but I don't see much room for the SSD, nor do I see much room in the slot where the SSD should be inserted.

Is that the slot to connect the SSD?

I repeat. I don't see a slot to connect the SSD.

Is it where the arrow points?

How big is an SSD? I looked for information, but there are several sizes. The space there is minimal.

I still don't see any room in the connector.

I hope you can clarify this question. Thank you.

PS: I haven't bought the SSD yet.