Can’t seem to load my saves from the real mednafen to use for this core and have it read correctly. I’ve beaten the game of wario land on the real mednafen but if I load the save on this core, it’ll say I’ve made zero progress.
RetroArch runs all of cores’ saves through the ‘srm’ files. Often, it’s just a matter of renaming them to match standalone’s format (that’s what I would try first here) but sometimes it’s more complex due to padding issues, etc.
the mednafen core saves it’s saves as .sav files though. Visually, the difference that I notice is that the real mednafen puts gibberish at the end of it’s save files before the .sav. Removing that and making it look like the vb core libretro saves is what I tried, and it’s not reading it correctly. Anything a hex editor can do for this?
Possibly. Open them both up and see how they compare.
wouldn’t even know what to do 
left is core save, right is standalone mednaf save
Renaming save file extensions from .sav to .srm is a mixed bag type of experience between emulators, sometimes it works and sometimes it don’t. Usually it works, but since I only played Virtual Boy Wario Land through Libretro I haven’t tried converting as you have.