Please help me determine which drive I can buy

I have the HP EliteDesk 800 G1 SFF PC.
I want to buy an SSD to replace the Hard Drive.

Question 1: Is this a 3.5" HD ?

Question 2: Do I look for SATA or IDE drive?

Question 3: What size can I buy? The HP website says "Up to 500 GB SATA hard drive; up to 500 GB self-encrypting solid state drive; up to 160 GB solid state drive' ; however, I already have a 1 TB HD in it and wonder why I can't go bigger with the SSD drive than 160 GB.

Information about computer: https://www.support.hp.com/us-en/document/c03832938

And Linux command information below:

michael@michael-HP-EliteDesk-800-G1-SFF:~$ sudo lshw -short
[sudo] password for michael:
H/W path Device Class Description
=====================================================
system HP EliteDesk 800 G1 SFF (K3N08AW#ABA)
/0 bus 1998
/0/0 memory 64KiB BIOS
/0/9 processor Intel(R) Core(TM) i5-4570 CPU @ 3.20GH
/0/9/a memory 1MiB L2 cache
/0/9/b memory 256KiB L1 cache
/0/9/c memory 6MiB L3 cache
/0/d memory 8GiB System Memory
/0/d/0 memory 4GiB DIMM DDR3 Synchronous 1333 MHz (0
/0/d/1 memory 2GiB DIMM DDR3 Synchronous 1333 MHz (0
/0/d/2 memory DIMM [empty]
/0/d/3 memory 2GiB DIMM DDR3 Synchronous 1333 MHz (0
/0/100 bridge 4th Gen Core Processor DRAM Controller
/0/100/2 display Xeon E3-1200 v3/4th Gen Core Processor
/0/100/3 multimedia Xeon E3-1200 v3/4th Gen Core Processor
/0/100/14 bus 8 Series/C220 Series Chipset Family US
/0/100/14/0 usb3 bus xHCI Host Controller
/0/100/14/0/1 printer HP LaserJet Pro MFP M127fn
/0/100/14/0/2 multimedia Webcam C270
/0/100/14/0/3 storage ImageMate 9 in 1 Reader/Writer
/0/100/14/0/4 input USB Receiver
/0/100/14/1 usb4 bus xHCI Host Controller
/0/100/16 communication 8 Series/C220 Series Chipset Family ME
/0/100/16.3 communication 8 Series/C220 Series Chipset Family KT
/0/100/19 eno1 network Ethernet Connection I217-LM
/0/100/1a bus 8 Series/C220 Series Chipset Family US
/0/100/1a/1 usb1 bus EHCI Host Controller
/0/100/1a/1/1 bus USB hub
/0/100/1b multimedia 8 Series/C220 Series Chipset High Defi
/0/100/1d bus 8 Series/C220 Series Chipset Family US
/0/100/1d/1 usb2 bus EHCI Host Controller
/0/100/1d/1/1 bus USB hub
/0/100/1f bridge Q87 Express LPC Controller
/0/100/1f.2 storage 8 Series/C220 Series Chipset Family 6-
/0/100/1f.3 bus 8 Series/C220 Series Chipset Family SM
/0/1 system PnP device PNP0c01
/0/2 system PnP device PNP0c02
/0/3 system PnP device PNP0b00
/0/4 generic PnP device INT3f0d
/0/5 system PnP device PNP0c02
/0/6 input PnP device PNP0303
/0/7 input PnP device PNP0f03
/0/8 system PnP device PNP0c02
/0/a communication PnP device PNP0501
/0/b generic PnP device IFX0102
/0/c system PnP device PNP0c02
/0/e scsi0 storage
/0/e/0.0.0 /dev/sda disk 1TB ST1000NM0033-9ZM
/0/e/0.0.0/1 volume 511MiB Windows FAT volume
/0/e/0.0.0/2 /dev/sda2 volume 923GiB EXT4 volume
/0/e/0.0.0/3 /dev/sda3 volume 8097MiB Linux swap volume
/0/f scsi2 storage
/0/f/0.0.0 /dev/cdrom disk DVD-ROM SN-108FB
/0/10 scsi5 storage
/0/10/0.0.0 /dev/sdb disk STORAGE DEVICE
/0/10/0.0.0/0 /dev/sdb disk
/1 power High Efficiency