Once you have a PS3 game up and running on the PS4, you'll need to play around in the menus a bit to get the save file onto your current console.

The Game Genie PS3 Save Editor will be available through Amazon, as well as “several local retailers,” for $29.99. The device is actually a USB drive containing the Game Genie setup program ...

If you have Warriors Orochi 3 you can import save data and any DLC you purchased into Warriors Orochi 3 Ultimate. Save data from the PSP version can be imported into the Vita release.