In order to rename VM file or a folder in ESX server we need to use a coomand as ESX server is builld on Linux core.
To do so:
Open an SSL connection to ESX server using Putty or a diffrent software.
Go to the file that you want to change.
Use cd foldername to navigate to the file
Use ls to view the files inside the folder
When reaching to the right folder use the command
mv oldfilename newfilename