Electrical – put a receptacle in a closet

Use plastic concrete/wall anchors with long pan head sheet metal screws. Pick the diameter whose screw matches the holes in the guide you are mounting. Use masking tape over the carpet and mark the hole locations using the guide you are mounting on the tape. Leave the tape in place while you drill the pilot holes. Drill through the carpet, pad and into the concrete. Make sure you drill deep enough in the concrete to completely sink the plastic insert.

Leave the tape in place or you will lose the holes. Insert the plastic inserts. If the carpet and pad is thick, be careful to push the insert into the hole as far as possible, then use a hammer over the hole to carefully seat the plastic anchors fully. They should be fully in the concrete. Place the door retainer over the tape and start the screws. Tighten the screws, drawing the retainer against the floor. Once in place, you can trim around the door retainer and remove any visible tape.

One simple thing to try that would not be too much work would be to re-mount the plastic bracket in nearly the same place on the center divider panel as before. Instead of the short screws use some bolts like these:

Select the bolt diameter that will work with the mounting holes in the bracket. Select bolt length sufficient to protrude through the bracket plus the thickness of the shelf side panel plus enough extra to engage the nut.

Drill suitable holes all the way through the side panel of the shelves at the location that you would re-mount the bracket. Clamp on a scrap piece of wood against the opposite side where the drill will come through to prevent chip out of the side panel on that side. Then mount the bracket with the bolts through the holes. On the opposite side apply some flat washers as pictured below on the bolts and then spin on the nuts. Tighten the nuts using a screw driver and wrench or pliers to hold the nuts.