Hello. How are you doing? I'll be happy to assist you.
I will size a pressure treated glulam for you.
Do you have storage in the attic?
The joists are 12' on each side of the beam, correct?
A 6.75" x 18" pressure treated glulam 24F-V4 will just barely work for L/240 deflection with the attic storage load.
6.75" x 16.5" without the attic storage load.
A 6x6 hem-fir no. 2 or better will work well. You should have full bearing to minimize any eccentricity in the post.
Hello. Do you have any other questions on this topic? If you could rate my answer, I would appreciate it.