You need to a onfluence-init.properties file insert into a WAR file of Atlassian Confluence.
$ echo "confluence.home = /var/atlassian/application-data/confluence" > WEB-INF/classes/confluence-init.properties
$ jar uf confluence.war WEB-INF
.
├── docker-compose.yml
├── Dockerfile
├── confluence.war
└── server.xml
confluence.war is a WAR file of Atlassian Confluence.
server.xml is a tomcat configuration file.
Run docker-command.