Well, you’re creating a new folder cause you’ve never backed up a save before. For the record, those folders aren’t the exact save the game uses. You’re merely “making a copy”.
so you can replace the file in “the copy”, then select restore, and bababoom
For VC Pokémon, just replace the sav.dat with a valid sav.dat of your choice, and restore. That’s it.
For Gen 1, and save file that PKHeX can read should be valid and can be renamed straightaway to sav.dat.
for Gen 2, you might need to hex edit the footer bytes; the time stamp stored by emu and cart/vc slightly differs.