If we'd all work together, I think we could accomplish our goal
What tense is it? Past or future?
The goal has been failed because they didn't work together, or
They will have a chance to accomplish them goal if they work together.
In this sentence, we'd is an abbreviation for we would, expressing possibility.
would modal verb (POSSIBILITY) (also 'd) used to refer to a situation that you can imagine happening:
If we would all work together, I think we could accomplish our goal
So, your second explanation is correct:
I imagine that we will have a chance to accomplish our goal if we all work together.
This conditional deals with “unreal, but likely” situations in the present or future. We call it “unreal” because situation we are describing hasn’t happened yet, and “likely” because we can easily imagine it happening.
it hasn’t happened yet (it’s unreal)
you believe it could happen (it’s likely)