Did you import the Bitcoin Core wallet.dat file into blockchain.info, or did you just create a brand new blockchain.info wallet?
If your blockchain.info wallet displays in the list of addresses the address where you sent the bitcoins when you sent them from virwox, then the bitcoins should already show up in that blockchain wallet. If the address where you sent the bitcoins when you sent them from virwox is not in the list of addresses in your blockchain wallet, then either you gave virwox the wrong address or you didn't properly import the wallet into blockchain.info.