New SSHD unreadable?

So i have a mid 2010 macbook pro and im trying to upgrade the HDD to a SSHD, but when i plug the SSHD in threw a external closure it gives me a error saying the Disk inserted is not readable by this computer and gives me a the options initialize... ignore or eject. Im wondering do i initialize then format or is there some thing wrong with my old MPB or the new SSHD?