A very simple way is to look at the sockets on the wall
Does it look like a plug you have at home?
Yes - this is a single phase plug you do not have 3 phase.
Does it have 3 holes in it (and normally is blue)?
Yes - this is a 16amp single phase plug you do not have 3 phase
Does it have 4 or 5 holes (and normally is red)?
Yes - This is 3 phase plug