Upgrading a VM’s VMware hardware version to the latest version is generally considered best practice. This is easy to do via the C# client or the web-client. If you wish to upgrade to a newer, but not latest, hardware version this can be tricky.

As highlighted in https://www.v-front.de/2014/02/how-to-uprade-your-vms-virtual-hardware.html, one easy way to do so is as follows on the ESXi host in question:

vim-cmd vmsvc/upgrade vmid vmx-10

where vmid is determined using something like:

vim-cmd vmsvc/getallvms|awk '{print $1 "  "$2" "$6}'

The appropriate hardware version can be selected from a useful VMware Virtual Machine Hardware Versions KB. The recent relevant versions are:

vmx-13: ESXi 6.5

vmx-12: Workstation Pro 12.x

vmx-11: ESXi 6.0 / Workstation 11.x

vmx-10: ESXi 5.5 / Workstation 10.x

vmx-9: ESXi 5.1 / Workstation 9.x

vmx-8: ESXi 5.0 / Workstation 8.x

vmx-7: ESXi/ESX 4.x