The range of walkie talkies is entirely dependent on where they are used and whether there are any obstructions such as hills, buildings between them.
All walkie talkies are capable of working over several kilometers provided there is good line of sight under ideal situations. But the range will be reduced by any obstructions such as walls, buildings and even trees.
You would need to know where the walkie talkies are used and that will determine if you would require a UHF or VHF two-way radios.
