Q:

How do I delete dropped items in a specific area?

How do I delete items in a specific area, because I don't want to delete everything.

A:

To kill items within radius R from point (X, Y, Z):
/kill @e[X,Y,Z,R,type=Item]

Replace X, Y, Z, R with numbers. For example, to kill all items within 20 blocks of (50, 64, -30)
/kill @e[50,64,-30,20,type=Item]

To kill items within a DX wide, DY high, DZ long cuboid starting at point (X, Y, Z) (most negative corner of the cuboid):
/kill @e[X,Y,Z,dx=DX,dy=DY,dz=DZ,type=Item]

Similar to above, replace capital X, Y, Z, DX, DY, and DZ with the values you want. For example, for a cuboid with opposite corners (100, 64, 100) and (150, 70, 130):
/kill @e[100,64,100,dx=50,dy=6,dz=30,type=Item]

