Screws stuck inside of Anchors, with shelving unit in between.
The type of plastic drywall anchor that you show on those screws can be removed by holding the anchor with a pair of pliers and then back out the screw with a philips screwdriver. After the plastic part has been removed toss it into the trash.

Note that that type of anchor is not suitable for hanging a wall shelf unless that shelf is a piddly small thing only intended to hold some small nick-knacks. Any other application should have the screws going directly into studs in the wall.