Your particular laptop doesn't have those old hard drives. The one it has is called a M.2 SSD, it should say right on it. It usually is 2x2 inches, or 1x3 inches and will specify the capacity.
Dell technical support, motherboard issue. Sent technician engineer. Replaced, issue must have to resolved. But facing problem, restart displayed on screen. I have contacted dell support os problem they said. Asked to send technician they said confidential you have get backup data if you want to if further proceed to install os ur data will be lost they said. So I tried to open laptop to take a backup of my hard disk then came to know no disk? Called technical support asked me wait 48 hours to investigate and raise an incident. Who is responsible if my data was misused.
Inspiron 5491 2-in-1, no hard disk?