Is the license letter from McAfee lost as well, if not use the grant number and login on the McAfee download site which will reveal the ePO license key.
If the old ePO is running at least ePO 4.5 you should be able to see the license key under Server Settings when logged on to the ePO console.
Check the ePO SQL DB on the old server, the last column in the table EPOServerInfo holds the License key in clear text.
Hope that this helps.
kindly use your grant no to download the McAfee ePO license key from www.McAfee.com
go to the enterprise option and select product download tab and enter ur gtrant no followed by -NAI then u can able to download your ePO license key.