Hello,
I can tell you already your system uses DDR 184-pin memory
but if you want more information
check out this site,
SDRAM, DDR2 and DDR RAM memory upgrades from Crucial.com
direct link to your specific model:
Computer memory upgrades for Dell Dimension 3000 Desktop/PC from Crucial.com
you don't have to buy from Crucial, just get the information off of there