Ram upgrade?

[Sam067]

Hi going to be buying a desktop PC - HP Pavilion 590-p0055na.

Specs: 

Processor Intel® Core™ i3 9100 (3.6 GHz base frequency, up to 4.2 GHz with Intel® Turbo Boost Technology, 6 MB cache, 4 cores) Processor family: 9th Generation Intel® Core™ i3 processor

Memory 4 GB DDR4-2400 SDRAM (1 x 4 GB); Total slots: 2 UDIMM Transfer rates up to 2400 MT/s.

I want upgrade the ram from 4gb to either 8gb or 16gbs.

What ram do I need to buy?

Is there a pacific what I need to buy? Or can I anything?

I've never bought ram before.

[Fanordi · Accepted solution]

Hello, your PC can in effect use 16 Gb of RAM, so you can install this capacity, in DDR4-2400 (you need to respect this frequency). 

However, I don't find the maintenance service or motherboard reference, so I can't know if your PC has 2 or 4 memory slots. 
If you have 4 slots you can keep your actual module and just add other 4 Gb modules, but if you have only 2 slots and want 16 Gb you need to replace your module by 1 16 Gb module or 2 8 Gb modules.. 

I will report this problem to HP. And I am sorry but I don't understand what is a pacific for you. 

[Prométhée]

Hello @Sam067  @Fanordi 
the solution is marked, but I don't understand your answer @Fanordi 
we have everything we need here ..
the pc is normally this

HP Pavilion 590-p0055na Product Specifications

and the motherboard:

motherboard specifications, Lincs

that said what is indicated is different for the motherboard

4 GB DDR4-2400 SDRAM (1 x 4 GB) (inside )

Memory upgrade information

• Dual channel memory architecture
• Two DDR4 UDIMM (288-pin) sockets
• Supports up to PC4-21300 (DDR4 2666)
• Supports 4 GB and 8 GB DDR4 UDIMMs
• Supports up to 4 GB on 32-bit systems

  note:

  32-bit systems cannot address a full 4.0 GB of memory.

• Supports up to 32 GB (with two 16 GB modules) and 16 GB (with two 8 GB modules) on 64-bit computers

  note:

  Maximum memory shown reflects the capability of the hardware and can be limited further in the operating system.

try :

Welcome to Crucial USA

[Fanordi]

@Sam067 I have been an answer from HP, so this PC have been the Lincs motherboard and it has only 2 memory modules. So you can install a second 4 Gb module for have 8 Gb, keep your 4 Gb module and add 8 Gb for have 12 Gb, or replace all with 2 8 Gb modules if you want to have 16 Gb. 
You can install 2 16 Gb modules if you want 32 Gb too but it is useful only for intense usage. 

[Sam067]

Thank you!