the water you want to use is zero TDS, aka distilled water, you can either distill it yourself or buy it. Do not use tap water. You can call the lube agencies and buy premixed coolant. Fuchs sell 5 litre cans of it, it used to cost Rs 1200/- in 2006 - I used to call them and they used to deliver. SIMPLE. Emarat also sell a premix of 30% conc (ideal for Karachi as it has more water to suck away heat). Mobil also have a coolant - its the old silica formula green stuff. As-Saqar also have a premix, would cost about the same as other premixes,
Caltex sells conc. - mix it yourself with distilled water, Do not buy the stupid little cans that are sold as Fuji, Osaka, Turtle etc. The only good japanese coolant available is made by Seiken, its a HOAT coolant and comes in large 4 litre packs, both conc and premix, dyed dark green - expensive and rare too.
NASA were selling a coolant conc which was good. is it still available? When I was in Pakistan - it also had 2 no. copies of it.
Whatever brand - the cost would be near to Rs 1500/- for 5 litres or anything good, anything lower than that and you know its not good. When you take your car to your mechanic/AC mechanic - they wont care and drain your coolant - SHOOT THEM IN THE NADS as its your hard earned money. As safe insurance, buy a little tub that can hold all coolant so it can be put back in. Do not trust their dirty oil change trays.