Please help me! important scooby doo question!! please!?

okay i love scooby doo ive watched it since i was a baby, i had a scooby doo room. i was obsessed. i still am lol. well anyway ive already seen all the scooby doo where are you?'s episodes. but im desperate to find out the name of the series that includes scrappy doo and scooby dum. there was also as i remember i think a series which only had scooby,shaggy and i think velma?? id love to buy those series on dvd but i do not know the names:) please help!! thanks! i appreciate it sooo much!(summary- i need to know the name of the stuff i listed above!)