We just moved from Atlanta, Georgia, to 2716 Hickory Blvd., Austin, Texas.

Is this sentence correct? I think it's not. I think the answer should be:
We just moved from Atlanta, Georgia to 2716 Hickory Blvd. Austin, Texas.
I don't think commas are needed after Blvd. and before to. Any guidance on address grammar rules would really help. This really confused me. I always feel when in doubt, leave the comma out. Which of the two sentences are clearer? Thank you for your help.

You do not need the comma after Georgia, but do after Blvd.

Which part of speech is the underlined word?

Mom and Dad stored the surprise birthday gift in the attic.

Both of the sentences can be considered correct, as they follow different styles of punctuation. The use of commas when indicating an address is a matter of preference and can depend on the specific style guide or formatting requirements you are following.

In general, when writing an address, you have a few options for punctuation. One common style is to include a comma between the street name and the city name, like in the first sentence: "We just moved from Atlanta, Georgia, to 2716 Hickory Blvd., Austin, Texas." This style adds a pause between the street and city names.

Another style is to omit the final comma, as in the second sentence: "We just moved from Atlanta, Georgia, to 2716 Hickory Blvd. Austin, Texas." This style removes the comma after "Blvd." and before "Austin," creating a smoother flow between the two elements.

In terms of clarity, both sentences convey the same information, so the difference is primarily stylistic. If you are following a specific style guide, such as the Associated Press (AP) or the Modern Language Association (MLA), you may want to check their guidelines on address punctuation.

If you are not required to adhere to a specific style guide, you can choose the punctuation style that you personally prefer or that looks clearer to you. Remember that consistency is key, so once you decide on a style, it's best to apply it consistently throughout your writing.