Your Shopify storefront address will be in the format your_shop_name.myshopify.com and is the default address provided to you by Shopify when you first opened your store.
If you can't remember your shop name you can find it by logging into your Shopify admin. There are 3 ways you should be able to find your shop name:
On your General Settings page in Shopify, your store name should be visible in the Store name field:
Alternatively, after logging into your Shopify admin, your URL should include your store name:
If you are unable to locate the correct shop name with the steps above, it may be under your Shopify domain name. It will have ".myshopify.com" at the end, and is often replaced by connecting a custom domain. It can be totally different from your store name and can't be changed.
To locate the domain name in Shopify, on the left go to Settings > Domains. Here it will list your store domains and you will want to find the Shopify managed domain which ends in "myshopify.com".
In the example below, the shop name is “acme-store.myshopify.com”.