Stocky by Shopify is an inventory management app that's included with Shopify POS Pro subscriptions. Stocky helps you manage your inventory by tracking your inventory levels, forecasting the inventory that you need, and suggesting which products you should order. To adjust your inventory levels, you can perform inventory counts and create inventory transfers.
Please note that Stocky is no longer available for installing from the Shopify App store
If you don't have Shopify POS installed on your store, then you can use inventory tracking in the Shopify admin for your products.