Dumping a PSP iso and getting scripts from it are rather different things.
Anyway it is much the same as anything else with a filesystem. Get your iso, unpack it (most would usually suggest "umdgen" https://www.romhacking.net/utilities/1218/
) and then you get to find the text. Names, extensions, sizes, relative search, tracing (not sure what PPSSPP, the main PSP emulator, has these days for debug support so you might need a suitably custom firmware PSP and have some fun with the memory readers on that), corruption, other mathematical/linguistic methods... all potential options here (I cover a bunch in https://www.romhacking.net/forum/index.php?topic=14708.0
. if you want, it is for the DS mostly but the principles apply here as well, though you are less likely to encounter compression) and dump it however you will.
I will note however that later translations might be more wordy (higher resolution screen and you could probably fit 1000 copies of the script in and most likely not trouble sizes), not to mention French generally is longer (there is a reason all those Arabic translations tend to opt for the French base ROM). The order might have changed as well. To that end not so many will backport scripts from much later systems as it is usually a lot of effort to either cut down the new one or expand the old ROM to fit it. English Final Fantasy tends to be the main exception as the English translations and official translators have something of a following but I don't know what goes for French (nor whether they went from an English base to French or straight from Japanese).