The first questions that come to mind are:

How far are the microcontrollers separated?

Are there any obstacles in between, and if so, of what kind (wooden, metallic, etc.)?

What is the necessary data rate?

To reduce your work, change the arduino kits with ESP kits. They can be programmed by the arduino IDE and they have WIFI built in. They cost less than 10 usd

You can use WiFi module for communication between two Arduinos (with ESP8266). For code, check how to connect 2 arduinos using WiFi. You can also use NodeMCU (inbuit WiFi is present) for this task.

There are many ways you can do to achieve that, as mentioned previously you could use the ESP-modules for wireless transmission with wi-fi capabilities or you could use bluetooth,BLE and nrf modules.

It totally depends on the type of communication, reliability, and the range you want to cover.

For wireless: you may use Bluetooth, BLE, WIFI, and LoRa.

If you are obliged to use Arduino, you have different alternatives:

For short communication range:

1. Use Arduino101 which has BLE integrated.

2. Use the Arduino UNO WIFI board instead of Arduino UNO.

3. Connect a Bluetooth shield to your Arduino

For wide communication range: Add appropriate LoRa module according to your area's allowed ISM band.

If you are free to use other boards than Arduino, as others mentioned, you may use NodeMCU, ESP8266 (different versions), Wemos D1 mini, etc,

Good luck!

Dear

I think you could use wireless modules with Arduino.

you could use this link:

https://digispark.ir/%D8%A2%D9%85%D9%88%D8%B2%D8%B4-%D9%85%D8%A7%DA%98%D9%88%D9%84-wifi-esp8266-%D8%A2%D8%B1%D8%AF%D9%88%DB%8C%D9%86%D9%88-%D8%A8%D8%AE%D8%B4-%D8%B3%D9%88%D9%85/