First, start with recommendations. Yes, simply ask your friends, colleagues in the shop, most likely someone has already collaborated with marketers and we can advise and give contact. Then the search is instantly simplified. You can also make a request in social networks about finding a marketer, and he will respond himself, or your friends / subscribers will recommend a specialist.
Secondly, if it turns out that no one can recommend, then start looking for a specialist in the profile groups of VK and FB (a social network recognized in Russia as an extremist organization) You can search for “targetologist”, “SMM", “blog of a targetologist", “traffic".