Most video projectors don't have outputs only inputs. You would need to use a VGA 1 in 2 out distribution amp.
The projector would connect to one output. The second would go to a VGA to HDMI converter and the converter would connect to a 1 in 2 out HDMI distribution box.
If the project does have HDMI then you can just convert VGA to HDMI and use a 1 in 3 out HDMI distribution box to feed all three screens.
There might be a single box to do all this but it probably have additional functions and cost more.