I did a search and found this guidance, Milner:
1) On the PS3 go to your virtual PS1 memory card.
2) Open the memory card and find your game save.
3) Connect your Vita to your PS3 and in the Content Manager on the Vita select "PS3 System -> PS Vita System"
4) Select "Saved Data / PlayStation"
5) You will see the option to select a PS1 virtual memory card
6) Select the card you want and it will open showing all of the saves inside
7) Select the save file you want and copy it over. That should do the trick.
That advice
was posted in August 2014; hopefully it remains valid!