Thanks for the response, I have found the solution, Instead of downloading from Microsoft I downloaded from another website and it seems working fine. So I wanted to upgrade Windows Server 2012R2 to 2019 Standard, I had to follow the below steps and it worked for me.
- Just took back up for the safe side.
- Download 2016 Standard ISO from <URL removed>
- Run setup.exe file from the Windows Server 2012R2 and select the Keep file and apps option.
- It Asked to run a couple of commands from X:\sources\adprep\adprep /forestprep "X" is your ISO mount drive or DVD Drive letter.
- Upgraded to 2016 Standard with these steps without any issues.
- The same steps follow for upgrading Server 2019 Standard.
So All good now :)