Equasis finds 622 ships with the simple search query "Maersk". Not all of them are container ships or nowadays owned by Maersk, but that could be a start.
This doesn't work too well as this search will bring up all ships that were ever connected with Maersk. For example, the first is Falcon; it used to be Maersk Constantia but was broken up in 2008.
It is better if you do a Company Search in Equasis.
This will list all the various Maersk operations, some are single ship owners only, others are Maersk management.
If you click on Fleet Info, you get all the info you need.
For example; Maersk Co Ltd company information shows this office is the owner of 24 ships, manager of 39 and ISM manager for 4.
Clicking on Fleet Info gives a list plus all details of 61 ships.