Hello Erick
If you want to connect three buildings, the first thing we need to know is.
Does building A (the building with Internet connection) have direct line of sight to buildings B & C, If yes this is a point to multi-point link.
If so, your setup will be one CPE, like the ENH500 on building A and one on both other buildings. You can use WDS Bridge mode on the CPE’s to create the connection.
If building A can only see building B, and not see building C then you have to set up a CPE on Building A, two on building B and one on building C. These are, point to point links.

Most manufacturers have a step by step setup, which might differ slightly depending on the model.
5Ghz CPE’s are the best for this. Most CPE’s will have the ability to see other 5Ghz signals in the area so you can pick the less congested channel.

These links work well, there is step by step instructions, datasheets and FAQ’s available on the manufacturer’s websites, so you can assess which product will suit you best.
Youtube videos will also give you some insight before you make your decision.

One important thing is to calculate the Fresnal Zone, as line of sight is not like a skinny lazer light. The signal balloons and this site link will assist you to calculate your CPE height requirements above objects along your path. https://www.everythingrf.com/rf-calculators/fresnel-zone-calculator. To calculate the distance between the buildings, use google maps ruler or line tool.

If you need further assistance, just ask here.

Thank you for your question.

I am Erick Villapando at the QCPU and I just want ask for your opinion regarding the easiest way to connect from building A to building B to building C since building A has already an iternet connection? Is it advisable to use wifi extenders of the business type of access point can do the job.

Thank you.