Windows Server 2019 Standard & Datacenter Licensing Policies for Virtualization Platform

2 physical processors with 48-Cores in each processor.

You'll need to license all for a total of 96 cores. If you use a DataCenter license the VM count is unlimited and AVMA keys can be used.
https://learn.microsoft.com/en-us/windows-server/get-started/automatic-vm-activation

for a Standard license you just re-license the 96 cores again for each additional 2 virtual machines.

but 2008 R2 is not included so that product will need it's own activations.

Licensing calculation is included in this document.
https://download.microsoft.com/download/7/C/E/7CED6910-C7B2-4196-8C55-208EE0B427E2/Windows_Server_2019_licensing_datasheet_EN_US.pdf

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Hi

How many CPU and it's just one server ?

You need to licence each physical core, and you need to cover the 20 VM.

In your situation you might be more winning by using a datacenter licence, as it dont have a maximum number of VM you can on your host.

You can try the calculator there; https://techlibrary.hpe.com/us/en/enterprise/servers/licensing/index.aspx. I tried the simulator with 4 CPU x 24 cores (For a total 96 cores).

In standard;

Base License Required
Windows Server® Standard (16 core) 1
Additional Cores To Be Licensed 80
Additional Licenses Required for Compliance
Windows Server® Standard Additional License APOS (16 core) 5
Windows Server® Standard Additional License APOS (4 core) 0
Windows Server® Standard Additional License APOS (2 core) 0
To License Additional Virtual Machines (VM's)
Note: 2 VMs are included in the Standard Base License once all physical cores are properly licensed.
VM's included when all cores are licensed 2
Additional VM's desired
Total VM's 20
Additional cores required to license additional VM's 864 additional cores need to be licensed
Note: Additional VMs/OSEs can be added in increments of 2 VMs/OSEs by re-licensing the total number of cores in the Server
Additional Core Licenses Required
Windows Server® Standard Additional License APOS (16 core) 54
Windows Server® Standard Additional License APOS (4 core) 0
Windows Server® Standard Additional License APOS (2 core) 0

In datacenter;

Base License Required
Windows Server® Datacenter (16 core) 1
Additional Cores To Be Licensed 80
Additional Licenses Required for Compliance
Windows Server® Datacenter Additional License (16 core) 5
Windows Server® Datacenter Additional License (4 core) 0
Windows Server® Datacenter Additional License (2 core) 0

Some general info

• Each host needs to be licensed.
• A minimum of 8 core licenses is required for each physical processor and a minimum of 16 core licenses is required for each server.
• Core licenses are sold in packs of two.
• Standard Edition provides rights for up to 2 Operating System Environments or Windows Servers containers with Hyper-V isolation when all physical cores in the server are licensed. For each additional 1 or 2 VMs, all the physical cores in the server must be licensed again.
• DataCenter Edition provides rights for unlimited Operating System Environments or Windows Servers containers with Hyper-V isolation when all physical cores in the server are licensed.
  AVMA keys can be used only when the host is DataCenter edition
  https://download.microsoft.com/download/7/C/E/7CED6910-C7B2-4196-8C55-208EE0B427E2/Windows_Server_2019_licensing_datasheet_EN_US.pdf

--please don't forget to upvote and Accept as answer if the reply is helpful--