There are clearly visible pegs for U brakes in the frame. At some point in the past, someone has removed those parts.
Any BMX U brake should fit, but you'll need inner/outer wires as well as two brake levers.
You cannot use a V brake, or disk brakes on this frame because the mounts are not there.
There's a chance the grips will not come off cleanly, you might need to replace the rubber grips as well. Sometimes they just slide off, can't tell till you try.
Clarification: this frame uses U Brakes whereas V brakes are more from mountain bikes and will NOT be suitable for this frame.
Notice how the pivot bolts are above the pads in the U brake (left) and below the brake pads in the V brake (right) This is why the two systems are not interchangeable.
You will need to buy:
two U brake sets, which will come with brake pads
two brake levers, a left and a right, with clamps sized to fit the handle bars, probably 22.2mm
possibly 4x bolts to secure the brakes to the frame - can't tell if they're still in the bike, or they might come with the U brakes.
two inner brake cables with ends to fit those brake levers.
some outer brake cable and ferrules.
It is possible to buy "brake refurb kits" that will have one brake's worth of outer and an inner, along with the ferrules and crimps. You can also get the outer in black or white or sometimes funky colours.
If this all feels like a bit much, look around your area for a Bike Cooperative who can help you learn, and provides access to their tools. This task can be done with normal garage tools, but a brake wire cutter+crimp can make it a lot easier.