How to connect docker images of ASP.NET Core (code first) and SQL server

I’m working with a project on nopCommerce, and trying to run it using docker images. There are two images, one is for nopCommerce and the second one is for MSSQL server. Here are the step I have followed,

1) Build docker image and run on a port 8080

C:UsersAdmin>docker run -d -p 8080:80 --name mystore nop420
ca626cc5ed4e3759a03e9645dcd374016a5d8f278ffede8e1345f851f9a82c7d

The project runs on the port 8080

2) Pulled out MSSQL(Express) Linux image from the Docker Hub

3) Ran it using command

docker run -e 'ACCEPT_EULA=Y' -e 'SA_PASSWORD=yourStrong(!)Password' -e 'MSSQL_PID=Express' -p 1433:1433 -d mcr.microsoft.com/mssql/server:2017-latest-ubuntu 

4) docker exec -it unruffled_tharp "bash"

5) /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P 'yourStrong(!)Password'

6) Created DB

7) Tried to connect MSSQL image using VSCode extension and it works

enter image description here

8) Passed the same connection string to the nopCommerce install page

Data Source=localhost;Initial Catalog=nop420;User ID=sa;Password=yourStrong(!)Password

But it gives an error

Setup failed: An error occurred while creating the database: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 40 - Could not open a connection to SQL Server)

I’ve tried using IP instead of localhost, adding port 1433 and almost everything from different forums though the error remains the same.

Edit: Here is network inspect

$ docker network inspect 6cb
[
    {
        "Name": "mynetwork",
        "Id": "6cb7171b74ee08a55d4ab8c9a26518bfb0a21ee5d8894300a7151453925f550d",
        "Created": "2019-07-16T01:13:46.4791178Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "ca626cc5ed4e3759a03e9645dcd374016a5d8f278ffede8e1345f851f9a82c7d": {
                "Name": "mystore",
                "EndpointID": "dbe46ebc4208bbce5d29c55c40bc0a0809ff3196da5ce7360c6e1a6771fcb7be",
                "MacAddress": "02:42:ac:12:00:03",
                "IPv4Address": "172.18.0.3/16",
                "IPv6Address": ""
            },
            "ca7b383ff3d5118aa15183728084e355619eb28b47d6e60c885a9e5c5af795ba": {
                "Name": "nostalgic_northcutt",
                "EndpointID": "6ec4ae69ba2586ce432471e82dcecc94e598e9f9c18f59ef2b557a317adf4736",
                "MacAddress": "02:42:ac:12:00:02",
                "IPv4Address": "172.18.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

Source: StackOverflow