Hello Selma,
There are several analytics services available to get an idea of the traffic on your site. Some are free others paid, some complex others simple to use. I think Google Analytics is free but it seems a bit complicated to use.
It all depends on the information you are looking for. For example, if you have "Guest access" on your Moodle site and want to know the number and origin of visitors, and the pages visited, you can use for example Web-Stat (free or US$ 9.50 per month) or LuckyOrange (free or US$ 18 per month) which are easy to use. These services also have options to make data collection GDPR compliant.
There are many other companies that offer this kind of service (do a Google search ) but the prices are often high.