The correct answer to this open question is the following.
Although you did not specify what destination you are referring to, and there are no options attached, trying to help we can say the following.
The two ways in which the sale of local souvenirs promotes the culture of any destination are the following.
Souvenirs and merchandise are an excellent way to promote a country, a city, or a tourist place. Visitors can buy souvenirs that are homemade by local people, helping to maintain an economic activity to generate income and pay taxes that benefit the community.
When tourists wear clothes, shirts, sweatshirts, hats, with the name of the place, they are promoting that tourist destination. When they buy commemorative plates, cups, mugs, glasses, posters, and exhibit them in their homes or offices as a decorative item, they are also promoting the touristic destination.