Improving the coverage 17 KM in 13 KM

i have area 17 KM in 13 KM clear area no buildings, main building need to receive the voice clear in the area clearly ,
i have 30 device of TH-UV8000D model + i have the pole antenna

i saw repeaters and duplexer can you help me to chose the right model from tyt and the equipment

You’re asking a lot. You need a repeater, filters and one/two antennas mounted geographically central to the coverage area required at a height above the ground where the horizon is the distance you need. Cost? DIY probably $1300 minimum, $2000-3000 typical. Dealer installed? $3000+. Licences and perhaps Government control likely in most jurisdictions. The repeater itself is expensive. Off the shelf purchase might be just under a grand, but the common ones can easily be double that. The filters can cost varying amounts - a simple type that uses a 10MHz split might be under 100, but if your Government allocate a 6.5MHz split, then the filter costs go up big time. If they specify even tighter splits, the filtering can be more than the repeater. DIY people need access to things like tracking signal generators and scopes/spectrum analysers and the skill to use them. I suspect this is NOT what you had hoped for. Due to geography, my UHF repeater has a 6Km service area for portables. the software suggests that 10Km would require an extra 10m of antenna height I cannot provide for planning permission reasons.