How to move wekan to other computer by docker?

I have read the official documentsMove Docker containers to other computer, but the documents are not detailed enough, and I failed in the end.

Here's how I do it:

1. Connect to server A
2. docker export wekan-app > wekan-app.tar
3. docker export wekan-db > wekan-db.tar
4. Connect to server B
5. docker import - wekanteam/wekan < wekan-app.tar
6. docker import - mongo < wekan-db.tar
7. git clone https://github.com/wekan/wekan
8. vim docker-compose.yml
9. Modify wekan image to wekanteam/wekan and wekandb image to mongo
10. docker-compose up -d error

$ docker-compose up -d
wekan-db is up-to-date
Creating wekan-app ... error
ERROR: for wekan-app  Cannot create container for service wekan: No command specified
ERROR: for wekan  Cannot create container for service wekan: No command specified
ERROR: Encountered errors while bringing up the project.