How to say "I am engaged in domestic trade" or "domestic sales" in English?

There are several sayings, such as the following one:

I work in domestic trade.

I'm doing local trade.

I'm in domestic/local trade.

It means domestic trade.

If you want to say domestic sales, then you can say:

I'm doing local sales.

I am doing domestic sales.

I am in charge of local/domestic sales.

I am a salesman in the local/domestic market.

All of the above have this meaning. It depends on how you apply it.

I hope I can help you.