Please where do I do this conversion to GPT, the server has the PERC H310 Mini  configuration utility. 
We purchased a Dell PowerEdge R320 Server which has three 2 TB SAS hard drives with the hope of configuring RAID 5. However after selecting BIOS mode and re-imaging with Windows Server 2012 R2( via a USB drive) we could not realise the full RAID 5 space as there was some unusable unallocated space( about 1.6 TB). Upon research on the internet, it was suggested that the server would have to be re-imaged with the UEFI option in order to create drives greater than 2TB and to make use of the unallocated space in disk management. However the following error is encountered when the UEFI boot option is selected: Boot Failed: Please ensure compatible bootable media is available. Use the system setup program to change the boot mode as needed. Strike F1 to retry boot, F2 system setup, F11 for boot manager. 　 Any help will be most appreciated.
Dell PowerEdge R320 Server RAID Configuration