I  read the OP's question to be asking  if all the pumps are  the same,  not are they supplied with the caravan.
Let  me answer the first  point.  There are  several  different manufacturers of caravan  water  pumps,  and there is  no standard design for the  fittings,  so you have to  get the correct  pump  and plug to  fit the  system fitted in your caravan.
If  you  are  buying  a brand new caravan,  the the  correct  pump  and lug should  be supplied with the caravan.
But  there is not telling  if the  pump  will  be supplied with  a second hand caravan. You  would  be wise to  contact  the  seller to  find out  if a compatible pump  is being supplied with the caravan,  and if  not then  ask the  seller to  get  one.
If th e pump  is one that  drops into  an external  water  container,   it might  be worth obtaining  a spare one to  take with  just  in  case. Having  a pump  fail  in  mid holiday is an annoying  inconvenience.
Do  read up  about  how to use the water  system,  becasue  with  a submersible pump,  its important  not  to  let th e pump  run dry,  as it  relies on the  water flow through the pump to cool the motor,  if the the water  runs out,  the  motor can over  heat  and damage the pump. 
Many  caravans use a pressure switch to  monitor the water  pressure and to turn the pump on and off automatically. Do  read up  on how to  adjust the pressure switch.