Hello Pooja Gurjar,
unfortunately, you cannot directly upgrade or transfer OEM licenses of Microsoft software (including Windows Server) to another type of license, such as from Standard to Datacenter. OEM licenses are tied to the hardware they were originally installed on and cannot be transferred to another server or machine.
If you need Datacenter licenses, you will need to purchase new Datacenter licenses separately. You might consider reaching out to a Microsoft licensing specialist or a Microsoft reseller to discuss your needs and explore your options. They might be able to provide better guidance on acquiring the correct licenses and possibly offer some trade-in or upgrade options.
If you have Software Assurance (SA) for those licenses, there might be some flexibility or options available through the Volume Licensing Service Center (VLSC).
Best regards,
Lei