please check my answer thanks :)

What is this sentence missing and where ?

One day my dad and his brother stop me if you've heard this story started on what they thought would be an uneventful drive to work.

I thinks it's missing commas

It's missing more than commas.

What phrase/clause can you remove to make the sentence flow smoothly? Before and after that phrase/clause that interrupts the sentence, you need dashes (make sure you don't use hyphens!).

http://grammar.ccc.commnet.edu/grammar/marks/dash.htm

thanks :)

Glad to be of help!

Great effort! You are close. The sentence is indeed missing punctuation marks, but specifically, it requires two commas.

To identify where the commas should be placed, let's break down the sentence:

"One day my dad and his brother stop me if you've heard this story started on what they thought would be an uneventful drive to work."

Now let's find the places where the commas are needed:

"One day, my dad and his brother, stop me if you've heard this story, started on what they thought would be an uneventful drive to work."

The first comma is needed after "One day" to separate the introductory phrase from the rest of the sentence. The second comma is needed after "dad and his brother" to separate that noun phrase from the rest of the sentence. Finally, a comma is needed after "this story" to separate that phrase as well.

Therefore, the corrected sentence would be: "One day, my dad and his brother, stop me if you've heard this story, started on what they thought would be an uneventful drive to work."

Keep up the good work!

Yes, definitely it is missing something.

In this case instead of using commas, I would use dashes. Parentheses can also be used .

One day my dad and his brother - stop me if you've heard this story - started on what they thought would be an uneventful drive to work.