ah shit. okay., so uh...
turns out the microsd card very likely has all the data ON it, but it's locked behind what is effectively a linux system so my pc can't read it. which means the roms are ON there, but inaccessable so I need... to either boot the Rpi3b+ up with the card in and hope it actually boots (it very likely won't :| ), or I need to find some way to make it think I'm accessing it on a linux machine, and then copy the files across... hm.
@Nine there are linux distributions intended to be booted from a flash drive with no need to make any changes to the computer you boot them on at all
@Nine in all likelihood your SD card is just formatted with ext4 or another common filesystem that's not compatible with windows. I think there's probably file managers you can get that can handle it though even without switching off of windows
@Nine https://www.diskinternals.com/linux-reader/ found this, don't know how good it is
@Nine file systems are weird and with how popular it is I don't know why windows doesn't natively support ext2/3/4
@Felthry because closed software systems = more control I guess, for microsoft that is, not for end users.
@Nine I don't think that really matters when it comes to file systems? the ways the various FAT variants and NTFS work are not exactly hidden
@Felthry You know, I HAD JUST found that utility, and I'm using it now, and it's wooorkiiing :D Fantastic though, thank you so much!