I know there is a topic about this but I thought I'd create a guide, step by step to help people understand better.
First of all, you need a PS2 Memory Card adaptor. I would highly reccomend getting an Official Sony one as I've had a few and found the official one gave me no problems where as the unofficial ones wiped a few of my cards.
Note: I dont think that the memory card adaptors support those different sized memory cards you could get like the 16MB for the Ps2 etc. Not entirely sure as I've never had one but Im sure my friend said it didnt work for him.
1) Plug in your memory card to your adaptor (either PS1 or PS2)
2) Plug the adaptor in to the PS3 in a spare USB port.
3) Go to game in the XMB Menu and scroll down till you get the Memory Card Utilitly (PS/PS2) Icon.
4) Now Ill assume at this point it has worked and you should see "Memory Card (PS1)" or "Memory Card (PS2)". If not, reset your PS3, and try again. It should work first time if it is an official but I know in the case of the unofficial ones that it took me a few goes, especially with the PS1 cards.
5) Press Triangle on your controller and Select Copy. Then confirm by selecting Yes for them to be copied to your Hard Drive.
6) You now need to select a name for the virtual memory card that the saves will be saved to on your HDD. I just called mine "Old RPG Saves" because thats all they were but obviously select what you want for yours.
7) The new internal memory card should now be showing in the XMB. You can select the memory card and see what game saves you have in there and copy them or do what you want with them.
You cannot however copy memory card saves back to your original memory cards sadly.
Now, to load your Internal Memory card to your game you need to follow these instructions:
1) Load your game
2) Once the game has loaded, Press the PS button on your controller.
3) Go down to assign slots and select it.
4) Now assign the memory card you want for the game, which in my case, is "Old RPG Saves" to Slot 1.
5) Press the PS button again to return to the game.
6) Now go to your in game loading options and the memory card will now appear and you can select your game saves.
Now this will only work for your specific region so you can upload a a NTSC game save to a PAL game. The PS3's themselves are region specific but the PS3 games arent.
Now lets say you want to load a new Suikoden II game and you would really like to load your PS1 Suikoden game save. Well im very sorry but you cant. The PS3 only allows the game save of the console the game is meant to be played on. This in a sense causes a little problem but at the same time, it doesnt. Now if you continue on to the following part of my guide I will explain the way around this....
Right, now say, you want to help someone out, give them your gamesave file, or just want to back it up, or want to show off to the world you scores. Here is what you need to do:
You need yourself a Memory Card/Memory Stick/ Ext HDD or something similar. In my case im going to be using an SD Card as my PS3 has the memory card readers.
To back up a specific gamesave file you need to:
1) Insert your memory stick in to the card reader or USB drive.
2) Go in to your PS3's XMB and select the Game menu and then select "Saved Data Utility" for PS3 backups or "Memory Card Utility (PS1/PS2)" for your PS1 or PS2 saves.
3) Select the file you want to backup/copy and click the triangle button.
4) Now you need to select where you want to copy it to, if you have a card inserted like I do, the SD Card will appear on the screen and select that.
5) It will now confirm that the save has been copied to your card etc.
Now you have backed up you gamesave and can do whatever you please with it.
Now for the way to transfer the game save from your PC back to your PS3, which is a little different.
1) You need to insert your memory stick or whatever it is in to your PC.
2) Open up the memory card and create a new folder called "PS3" (without the "").
3) Inside that folder you need to create another folder called "EXPORT" (again without the "").
4) Within that folder you need to create another folder called "PSV" (finally without the "")
5) Now within the PSV folder you need to copy the file/s you would like to put on to your PS3.
6) Insert the card in to your PS3.
7) In the XMB go along to the Game menu and select the Memory Card Utility (PS1/2).
At the very top of this page your memory card or whatever you have used should be at the top of the page. Now click on that and the game saves will appear.
9) Click Triangle and select to copy them to your hard drive.
10) Now you have successfully transferred your game saves to your hard drive.
Please note that the only game saves you can transfer to the PS3 at the Virtual Game saves generated by the PS3 (.psv files). No other files will work so the game save has to have come from a PS3 originally, unless you use the method of transferring straight from a memory card!
I hope this guide has helped and if you have any questions please just feel free to ask!