Ok, talk with you later! I'll leave this here if you want to try tomorrow. Or you can just reply that you want to try the PC way.
For this test, I formatted my SD card to NTFS (unreadable to Vita) and I got the Vita to format the card and mount it so I could copy to it. This is what I did.
In system/devices/storage devices
I set ux0 to memory card or internal storage whichever you have.
I set uma0 to SD2Vita.
I reboot.
After reboot
I went to system/devices/storage devices.
I opened the developer menu.
I used the direction arrows to highlight TexFAT format and I pressed x.
I reboot.
After reboot
I entered vitashell and uma0 was mounted and ready to copy ux0 to it.
If you made it there, then you can just copy all from ux0 to uma0 like I mentioned above and then.
In settings/devices/storage devices.
Set ux0 to SD2Vita.
Set uma0 to default.
Reboot.