You can place these scripts in the server/bin folder of your Loopback 3 Application for automigrate and autoupdate funtionalities.
This will migrate your models and relations to the database, however it will drop table data.
npm run server/bin/automigrate
This will migrate your models and relations to the database, without dropping table data.
npm run server/bin/autoupdate
*N.B For this script you may have to manually stop its execution by pressing [COMMAND | CTRL ] + C.