IIRC when looking into this originally, there are multiple tools necessary due to additional metadata on the MCs: mcpaste for PS1 saves, psupaste for PS2 saves, and the PS3 uses an entirely different format that needs to be converted prior to use (I don't remember if you need to jailbreak to get the keys for this)
Felt there was a bit too much manual stuff involved which could allow human error to come in and mess something up. I did do a copy + psupaste to the internal HDD on a new partition just in-case, but there was no way I was going to risk copying those back onto my only memory card to test if it actually was done right 😅
The original MC was near full as well, so it's pretty nice to also be able to spin up new ones when needed (to be fair I believe OPL has a similar feature built in, although some games may freeze using it)