Using QCMA of course.
1. You will need a SaveData from PSP Game. ( Dont need to be your own, you can use from another console).
2. Put this savedata into your folder
PS Vita\PSAVEDATA\xxxxxxxxxxxxxxx
In my case i used King of pool.
PS Vita\PSAVEDATA\xxxxxxxxxxxxxxx\NPUH10053
3. So put your vkp into a folder. You can create a folder inside your savedata.
In my case i create a folder
PS Vita\PSAVEDATA\xxxxxxxxxxxxxxx\NPUH10053\vpk
And I put 2 games inside ( 3Gib total ).
4. IN QCMA refrest database
5. Open content manager in vita and transfer the Savedata.
In Molecule go to :
ux0 : Pspemu/PSP/SAVEDATA
Find your savedata, inside you will see your file.
It's best solution, because you can transfer a lot of files, like .bin, or small one etc.