This Hardy Boys series comes after the original series. It's the "new" series that came after it and everything listed it's all in numerical order that the series comes in. The following are the trilogies that are part of the series: 

Murder House Trilogy (Deprivation House/ House Arrest / Murder House)

Double Danger Trilogy (Double Trouble / Double Down / Double Deception)

Galaxy X Trilogy (Galaxy X / X-plosion / The X-Factor)

Killer Mystery (Killer Mission / Private Killer / Killer Connection)

Lost Mystery (Children of the Lost / Lost Brother / Forever Lost)

Deathstalker Trilogy (Movie Menace / Movie Mission / Movie Mayhem)