Hi Kharthi
For Upgrading current system to ERP6 EHP7 you have to follow the three stesp
1. From the current OS/ DB & SAP level upgrade to ECC 6 / NW 7.00 SP level 31 (You can perform this on your Old system)
2. From ECC 6 / NW 7.00 SP level 31 (On old server ) you can perform the SAP Homogeneous System copy(Backup/retore or detach/attch method) from the old to new server with Windows 2012 & MS Sql 2012. (using the SWPM)
SAP system upgrade and System copy refer the SAP guide from http://service.sap.com/guidefinder - Select you OS /DB & Sap version
3. From the new server you can upgrade to SAP ERP 6 EHP7. before that in your landscape if any other SAP system connected in the ECC. check the interoperability with SAP version, refer the SAP Note with PDF
1388258 - Version Interoperability within the SAP Business Suite
BR
SS