Google "pole to wood bracket" and you'll see a ton of them. Home Depot or any hardware store could help you, too. In my experience, most hardware stores have someone who comes over to help the clueless and they usually assume women are. I've done very well saying things like, "I need a thingy that will do this".

This was my first Google result.:

Wood to Steel Pipe Grip Tie 1 5/8" Round Post to Wood Fence Bracket - Galvanized | Chain Link Fittings

Thanks. I’ll try google. i’m trying to avoid grip ties, because it would ruin the look of the arbor.

Angle iron?

An image or two of the arbor and fence panel will help others help you.