If that is from hokagestore.com, it's probably some experimental extra code. Alidropship sometimes tries things with their own stores before adding them to the plugin and/or themes for everyone else.
Maybe one of the staff will pop along here and confirm that.
If you used Woocommerce ... you can do it as described here ...
https://businessbloomer.com/woocommerce-show-number-products-sold-product-page/
Although if you had a new store and have not got many sales ... I'd advise against using it until your store has got a lot of sales.