The Sims 3 has to be decrypted to run on almost any cart. (Except the expensive high-end ones)
use a program called encryptds (Not on filetrip)
I do know that it can be found in RetroGameFans firmware pack, under "Extras".
I was going to DL the firmware for your card and further instruct you on wich RGF firmware will work on your card, But, your cards page has me downloading at 9kbps.
srsly tho if ur booting to white screen you just need to Decrypt it with Encryptds. put it in the same folder and run the program.then put the rom back on the card. you wont notice any changes to the rom that are visible to the eye, but just trust that the program worked.
don't be to excited or upset over The Sims 3 for DS, its not worth playing. lol You play as a single person. you can marry one of the sims in town to have two people but, that just makes the game worse lol
I Finally got your firmware downloaded!
It seems your card is a DSTT Clone. You may be able to simply drop standard DSTT Firmware onto your card and rename TTMENU.DAT to R4i.tp
Good Luck to you!
If your new to the scene, its definitly not as confusing as it seems. You'll have it all figured out after a couple of days of tinkering.
EDIT: Oh! it works for a few seconds and stops? You may just need to update your firmware to use RetroGameFans. Your card is a DSTT So just do as i instructed above. Copy the YSMenu firmware onto your card, and rename TTMENU.DAT to R4i.tp You can still try what i wrote above, but if it boots its likely not your problem. if it just shows the Loading screen and stops there, then you do need to update your firmware.