My advice is don't buy preconfigured units. Ubiquiti radio bridges are easier to set up than IP cameras because they don't require any browser plugins or figuring out unpublished RTSP URLs or similar nonsense. The procedure for setting up a bridge using ubiquiti radios is very well documented online. You'll benefit from learning how they work.
You could achieve your goal with two pairs of point-to-point bridges (4 radios), but you could also do it with 3 radios in a
point-to-multipoint configuration. (be sure not to skip the step where you set up a WPA2-AES key!)
Just configure the radio at location
2 as "access point", and the radios at locations
1 and
3 as "station". Obviously the radio at location 2 needs to have a wide angle antenna (I think any Nanostation model should be fine) and be aimed at a point between locations 1 and 3.
If you can guarantee a perfectly clear line of sight, you will probably get the best speeds with 5 GHz radios instead of 2.4 GHz. I'd recommend three
NanoStation 5AC Loco (Loco5AC), but be aware those don't come with power injectors like the older models did so you need to
buy those separately if you don't already have some spares. The Loco5AC doesn't support standard PoE like you'd use for an IP camera, so you can't just power them with a standard PoE switch.