power socket

[Coolhandan]

HP Z1 All-in-one Workstation has a 3 prong power socket on workstation monitor do i just plug the power cable to the 240v socket direct or is it 19 volt or so on help

[BeemerBiker]

This is your Z1 power supply

https://www.amazon.com/Genuine-HP-Workstation-656522-001-650503-002/dp/B078QD2JV7

sorry - I just re-read your question and the problem is the monitor not the system

what is the name / model of the monitor? 

If the power cord for the monitor has a switch with writing that says 110 or 220 then select the correct voltage. If not (no switch present) then look at the instructions / warning on the device (wall wort?)  It should be autos witching as virtually all modern power supplies are.  If the cable does not match your wall socket then you need an adapter.

If in doubt please post a picture of the power adapter and tell what country you are in.

[SDH]

In all the HP workstations I have worked on the power supply does not have a switch for European vs US power selection... that happens automatically within the electronics of the power supply itself.  Attached as a PDF is your technical/service manual, and also a picture of your power supply's label... note the wide range of voltages it accepts.  It is the cord that is important for you... you want it to be compatible with your nation's power receptacles.  Once you get that end right the other end that plugs into the HP workstation is standard. 

There are not two power inputs on your workstation.  Only the one behind your monitor's bottom corner that you refer to.  Save the manual below for future reference.

[BeemerBiker]

There must be a language problem here.  You mention the "monitor"  and 19v adapter but show pictures and documents of the "Z1 system" and the 110-220 power supply.  Those are different.

As you mentioned (and is shown in the picture), the power supply adapts to 110 or 220 and comes with a UK or EU power cord.

On one occasion I bought a cable like that by mistake and it is useless in USA.  I am not an electrical engineer and do not know how to ground computer equipment that does not have that 3rd pin on the cable.  If the socket has the 3rd pin that mates with the plug then you are ok.  One of my sons is in Germany and the entire Army base is wired for 110v 'USA style" so he does not have a problem nor can I ask him for advice.  I think he bought a German kitchen appliance and had to get a converter to USA.

[SDH]

No language problem here... respectfully, there is such a thing as the HP Z1 All-In-One Workstation which the OP refers to as his own, and this combines the monitor and the computer in one... and here are pictures of that from the side and from the rear.  Also there is no external 19V power supply involved:

The technical and service manual PDF I attached for the OP has more pictures showing the single place to plug the power into... be it 115VAC or 220 VAC in the US/Europe, respectively.  Very nice combined workstation... HP's response to the iMac.