Looks like your case is for a uATX motherboard, and the motherboard is a MATX... both uATX and MATX mean Micro ATX but the mounting hole location is the only difference... you can either use a plastic spacer/screwless standoff.. or drill a hole and thread it with a Tap to take the brass standoff, or use the brass standoff upside down bolted to the motherboard with an appropriate size nut.
Some Power Supplies have the right size plastic spacers or try finding them in a computer supply store.. and if you can't find them, you can buy the Plastic Screw-In PCB Standoffs and cut the threaded part off...