The washers are either concave or convex and meant to go together so that they can have a slight range of movement. In other words the convex nestles into the concave.
The configuration depends on how best the pads in the caliper aligns with the disc. If you hold the caliper in the optimum position without washers you can get an idea if washers are needed under the adapter which is usually the case and how many. It is also possible to have washers on top of the adapter.
Assemble with all washers and bolts but not all the way right. Apply pressure to the proper brake lever and tighten the bolts. This should align the pads correctly but might take a few tries.
Should be you tube videos on this procedure also.