My server is offline and cannot be patched online automatically.
I found a lot of patches on Product Patches - VMware Customer Connect, such as: VC-6.7.0U3j-Appliance-Patch, VC-6.7.0U3i-Appliance-Patch
If current version of my vsphere is VC-6.7.0U3k-Appliance, should I install all later patches to the server? or I just need to apply the newest patch is enough?
The patch and update packages in VMware vSphere are cumulative.
Attached link about the versions of vCenter Server Appliance
In practice, it is usually recommended to use the penultimate and not the last one available. If it is not mandatory to apply the latest one due to a specific problem.
Another rule of thumb is to always have a full backup.