Query record from external database and automatically populate form fields?

What would be the best way to query an external database and populate all the fields in a form?

Here are the steps I've completed so far:

1. External database connected as a data source

2. CDT created and entity has been successfully mapped to data source

3. Form has been created using the CDT as rule inputs, and with each form field's "Display Value" and "Save Input To" set to the respective field in the CDT.

In the screenshot below, the Barcode field is the primary key in the CDT and the external database. I want to be able to scan in a barcode number and then automatically populate the remaining form fields with the data record from the external database.

What should be my next step?

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