To delete a store you first need to remove all products from that store. You can either move the products:
https://support.getdpd.com/hc/en-us/articles/360021274851-How-to-Move-a-Product-to-another-Store
Or delete the products:
https://support.getdpd.com/hc/en-us/articles/360021021352-How-to-Delete-a-Product
Once the products are removed, the store URL will change to a remove store link on the product list, as shown in this screenshot:
