Hello engro;

Start by looking at the contents of this discussion, and consider that the techncal replies are a sample of the information you need to master to make your IWLAN system work:

https://support.industry.siemens.com/tf/ww/en/posts/wireless-communication-for-4km-distance/58409?page=1&pageSize=10

Elements you should think abour is transmission power and antenna gain, line-of-sight installation (or not possible), transmssion frequency vs range...  The following manual from Siemens explains all these considerations quite well, and shows the different configurations for various SCALANCE transceivers.

https://support.industry.siemens.com/cs/ww/en/view/90880063

For solutions from 3-rd party vendors, you could have a look at this offering (there are more providers available on the web):

https://www.dlink.com/en/products/dap-3712-20-km-long-range-80211ac-wireless-bridge

Hope this helps,

Daniel Chartier