psv-save-converter VS save-decrypters

another option, once you have the .PSU file, is to convert it to ps3 native format PSV using Apollo save tool (ps3) or the psv-save-converter tool (pc/mac/linux).

You need to find enthusiast GitHub projects like https://github.com/bucanero/psv-save-converter that does this for the game in the direction you want. But it's mostly a not possible.

You can download the tool here: https://github.com/bucanero/psv-save-converter

Then if you want to use them on a PS3, you'll have to convert ps1/ps2 saves to the ps3-specific "PSV" format. (with a tool such as https://github.com/bucanero/psv-save-converter on your computer, or using Apollo save tool on your PS3)

if you have single saves for ps1 and ps2 games, you can use psv-save-converter (https://github.com/bucanero/psv-save-converter) , and convert them to the official PSV format expected by the PS3. The tool supports many save formats:

if you want to do it on PC, you'll need to use a checksum fixer tool. There was one original tool by RedEyeX32, or a simple command line tool I made later when testing some Apollo features.