Have Dell Inspiron 3670 computer and wanting to add a larger hard drive. What can I use and will I need cables and sled rails etc?

hdds are mounted on chassis wall.  no rail or caddy.

you need SATA data cable long enough between HDD and motherboard.

power SATA cables are probably already there inside case.

https://www.dell.com/support/manuals/en-us/inspiron-3670-desktop/inspiron_3670_servicemanual/procedure?guid=guid-935fe882-1f1d-44a3-8b52-07129708f376&lang=en-us

https://www.dell.com/support/manuals/en-us/inspiron-3670-desktop/inspiron_3670_servicemanual/procedure?guid=guid-6542ccf2-87db-413e-adf1-95841c16cc93&lang=en-us