Do you sell boxes to ship back ?

I've not seen boxes for sale but have seen people use boxes from the box recycle containers under the table side facing the lockers.

If you need to return something, everything is provided by the store free of charge.

Boxes are not available.

I used the supplies like tape and scissors but didn't see any boxes.

You can actually drop things off there, no actual box needed

I don't think so. It's a pickup point, with lockers.