Hi, it is difficult to advise exactly what pump you need without more information; e.g. what is the uplift from the tank to the pump, how much water you need to move, how quickly, whether the distance between the points is in a straight line, what size are your hoses etc. etc.
However, as a rule of thumb, the maximum head capacity of the pump can tell you what the pump can do in terms of; suction height + uplift. For example, if you needed to draw up water 5 metres from the water source to the pump, then move the water from the pump up a gradient of 15 metres, then you would need a pump with a maximum head greater than 20 meters (5 +15).
Also remember that there will be a small loss of head capacity through general friction, so your first consideration is a pump with head capacity greater than 20 metres, then secondly what flow rate (litres/min) you require - this is where the pump charts come in handy (on the product brochures) as the water flow rate diminishes with the height.
Depending on your suction height, I would be inclined to look at a Honda or Subaru powered 2" or 3" Transfer Pump that has a head capacity of around 30-35 metres and flow rate of around 500-600 litres per minute. If your suction height or flow rate requirement is larger, then you'll need to look at a larger pump.