Dell Poweredge and VMWare Hypervisor

Hi; I already have installed Hypervisor at Dell Poweredge R620, I would try to install other one, now it may be VMWare vSphere Hypervisor. 

Unfortunately; without checking compatibility matrix, I downloaded the Hypervisor 8.0, which may not work, so I did not even try to install it. 

Then I saw that for the Poweredge R620 there are few options available but the Hypervisor main version is same: 6.5 U3; 6.5 U2; 6.5 U1 and 6.5. Finally, I was just able to see this version in VMWare Downloads section as all options for downloads were grayed, dismissed. 

After that I saw that there is possibility to download the 6.5 at Dell site, DellEMC_Customized file. 

Then I downloaded it. 

Now, there is the problem, I do have Licence key saved for the previously saved (not installed) version 8, downloaded from VMWare; but I do not have the Licence key for the 6.5, downloaded from Dell site and, seems that there is no possibility to get Licence key for it (as mentioned, the download of the Hypervisor is not possible, so there is no page where the key would be visible and then saved). 

As I saw, after Hypervisor 7 version (including that one as well); VMWare changed the Licence methods, which would mean that the Licence may have different pattern and, for sure, version 8 Licence key cannot be used for the version 6.5 (I did not try). 

The VMWare vSphere Hypervisor is freeware, anyway it needs to be Activated, Licenced using the key. So, Licence key is to be there. 

Question is: Has anybody experienced similar or the same problem and what would be solution?

Thank you.