In order to find out how many people contacted you through the chat from the ads, you need to install a tag along with your Tawk To code.
To get the code just follow the steps below:
Step 01: Log in to your Tawk To account.
Step 02: Enter the dashboard: https://dashboard.tawk.to
Step 03: Click Admin
Step 04: Copy the Widget Code
After this step, you should send this code to your programmer to install this conversion event on the website.