Steps 1 and 2 basically copy mongo 3.6 data into a new dir mongo_4 but mongo image of version 4.4 does not accept that data. So I had to perform the following steps:

Launch docker container with mongo=3.6 dump data using mongo dump Launch docker container with mongo=4.4 and empty mongo_4 data dir Restore the dump data using mongo restore
This made sure the data is now compatible with mongo 4.0 or greater