Change "lupu" to "precise" in the savefile name.
Or make a save with precise and rename your old save
to whatever it is named.
Dont try to "convert" it thats something different.
A save is a modified .sfs labeled .2fs or .3fs or 4fs
relating to ext2/3/4 while the .sfs converter converts bwtween
squashfs versions 3 and 4.