Hi @Anonymous ,
I made a template for your reference:
Here is tableA:

Here is tableB

Before creating a flow, we need to get the logical name of the ordernumber column

Here is flow:
The way we use characters to stitch html tables

Use filter rows for tableB, where the logical name of tableB ordernumber is required

Fill the filtered values into the table

Email the html table

Here is result:

Best Regards
Cheng Feng