Here are all parts you need to build the brackets.
First Place Part_B_1, Part_B_2 and Part_B_3 on your IKEA Malm chest as shown in the picture below.
Screw the parts together by using 4 M3 x 20mm screws und 4 M3 nuts.
Slide Part_B_7 and the mirrored version of Part_B_7 into the rail.
Insert Part_B_4 and the mirrored version of Part_B_4.
Place Part_B_6 on top of Part_B_4 and fixate it with a M3 x 8mm screw.
Redo all steps.