I think there's some confusion over the paths involved.
Lets say your docker-compose files are in
/opt/xibo as we suggest.
If so, your database backup file needs to be
There's no need to try and change the database name. cms is the default and that's what the system expects with a local database container. What the database was called on your old system is inconsequential.
You need to remove the currently running containers as they are configured in correctly. To do so:
docker-compose -f cms_custom-ports.yml down
Check no containers are left running with
Assuming there aren't, then remove the database container files
rm -r /opt/xibo/shared/db
Now, ensure that your library files from the old CMS are in
/opt/xibo/shared/cms/library, not somewhere in
/var/www as you suggest.
Now get fresh docker-compose files from the 1.8.3 release (there seems little point in going to 1.8.2 now that 1.8.3 is released, and fixes nearly 100 issues!). Do not edit the database information. It is correct as it is shipped. All you need to edit is the config.env file to ensure you've set a password for MySQL, and if you want to use a non-standard set of ports, then copy the cms_custom-ports.yml.template file to cms_custom-ports.yml and edit the webserver or xmr ports as you wish.
docker-compose -f cms_custom-ports.yml up -d
The old database will be imported and after a time you will be able to log in. Keep in mind that with a large number of layouts, it can take a very long time for the upgrade to run. The upgrade will run to completion before the webserver is started.